The only problem is that it's just not a very good thought experiment. You're suggesting someone who becomes a Christian, never has a day of unhappiness in his life, and wants other people to have the same. It seems to beg the question, since the omission of anything bad happening to the man is glaring.

But to answer the question, the defect in the man's thinking would be that he assumes that all humans would benefit from the exact same thing that he does. In short, his evidence for his cultural truths being correct is that he enjoys his culture.

Okay, insert common life barrier here.  I just didn't mention anything because I'm not going to write an entire autobiography

My objection is more that if this guy spends his whole life affirming his choice of lifestyle, it could just be an instance of confirmation bias mixed with a particularly lucky life.

I don't think it's so much the quality of his life, I think it's more of him and others taking action for a positive effect.

 I'm going to try for about the tenth time to figure out the lynchpin in your misconception of religion.  Why I am filled with optimism everytime I think of a new possibility, I don't know.  Go ahead and ignore this one, too, and I'll see if I can think of something else.  It's a good mental exercise for me.

Ok, try this on for size:  You're defining words like "effect" and "action" and "positive" so loosely that you can't really help but drag yourself into a mire of incomprehensible claims.  Our last discussion of cause and effect got me thinking of this.  So, here's the example from your thought experiment:

Bob was unhappy, or at least, not happy.  Then he became a Christian.  Now he's happy.  Becoming a Christian made him happy, right?  

Here's the thing -- what was Bob unhappy about?  What changed in his life after he became a Christian?  Which happiness-inducing events were tied directly to Christianity, and which were conflated with Christianity by simple human nature?  Was Bob lonely, and did finding a group of friends at the Wednesday night pot-luck dinner give him a better sense of self worth, which made him happy?  Did he meet a group of single girls who accepted him because he was a new Christian, when they wouldn't have accepted him otherwise?  Did he get asked to head up a project for building a new sanctuary, which is right up his alley, since he was an out of work construction worker?

Your thought experiment ignores the unique aspects of religion, and simply lumps any activity, belief, or feeling felt by a Christian as "Christian."  Of course, using this kind of loose thinking, anything that anyone finds which precedes happiness "caused" them to be happy.

In contrast, I attempt to isolate very specific elements, unique (or particularly relevant, at the least) to religion/Christianity, and look at very specific consequences of those elements existing.  For instance, I proposed that for the singular and unique reason that Christians believe prayer works and is good, most Christians pray.  This is a direct line from a unique element of religion to a unique behavior.

Similarly, I think I could draw a pretty straight line between the belief that abortion is murder to intense social pressure not to have an abortion.  Duh, anyone?

Our ability to draw straight lines is hampered severely by the fact that there really aren't very many things unique to religion, and most religious people behave similarly to non-religious in most ways.  The trick, then, is to find ways in which religious people's behavior is substantially different than non-religious people's.  Similarly, if we are evaluating emotions and beliefs, we need to figure out what the religious feel and believe that the non-religious do not, and vice versa.  

Your thought experiment doesn't account for any of this.  From what you've said, Bob's happiness could have come from any number of changes in his environment that are correlated with but not caused by the specific religion itself.

Why don't you try thinking about this in reverse.  Find a belief that comes uniquely from religion, and then create a thought experiment in which Bob finds this belief, and the belief itself is the thing that causes change in his life.  If you do this with an open mind, i think you'll start getting a grasp on specifically how I attack religion.  I'll get you started:

Some Christians believe that humans are unique in the universe and have unique potential for good.  Ok, except that's what secular humanists believe.  Not unique to religion, so it doesn't count.

Some Christians believe that every life is sacred and that if we respect our lives as sacred, good things will happen.  Ok... except... yeah... secular humanists believe that, too.

I've got one that might work...

Some Christians believe that if you pray for anything you want, you'll get it if you have enough faith.  Let's say that Bob prayed to win the lottery, and won the lottery.  He paid off all his debt, moved to Tahiti, and now he's lounging in the sun with a Mai-Tai and enjoying retirement at 35.  He's damn happy.

Did the Christian belief in prayer cause his happiness?  I feel pretty certain that Bob's still a devout Christian.  After all, winning the lottery is extremely unlikely, and he did pray to win right before he bought his ticket.  God hooked him up!   I'll be honest, you might have a case here.  If Bob wasn't going to play the lottery, but he firmly believed that if he said the right magic words, he'd win, that belief might cause him to win the lottery.  You can't win if you don't play, after all.

But even here, how much of his happiness is attributed to that specific belief?  Is it fair to say that prayer made him happy or that money made him happy?  Put more succinctly, how many more times since then has Bob prayed for something specific and highly unlikely and had it happen immediately afterwards?  Also, what other Christian beliefs does Bob have?  Does he pretty much ignore the stuff about fornication and drunkenness?  Does he go right ahead masturbating and cursing (except maybe for not saying Goddamn anymore), etc, etc?

I'm not trying to play some kind of No-True-Scotsman here.  I'm trying to show you that religious effects from being a Christian are a lot more specific than you're trying to make them.  Put fifty million dollars in most people's hands, and they're going to be happier than they were yesterday.  That's not a religious effect.

Here are the things I can think of off the top of my head that Christianity teaches, which are distinctly opposed to the empirical truth of the thing:

1) Man is sinful, and must overcome his evil nature.

2) Man cannot hope to do this.

3) Sex is bad unless it is within a monogamous marriage.

4) Masturbation is bad.

5) Lust is bad.

6) God will either answer us or not when we pray, and no matter what we want, his will is what will happen.  (I think you ought to run with this one... there are probably a few happy stoics in the world.)

Ok... I just looked at the clock, and I have to run, but you get the idea, I think.  What I'm attacking in religion is the specific non-scientific beliefs, which, when translated into actions, result in typically dysfunctional situations.

I guess my response would be...great.  But if not Christianity he might have done more good by getting sucked into doctors without borders, or UNICEF or something.

Just because he is better than he was before, does not mean he is the best he could have been.  By following a specific religion he has decreased the value of his monetary donations, because of church overhead, and decreased the value of his time donations because, presumably, he spends part of his charity time spreading religion instead of helping people.  Plus, he might be spending time fighting for moral value type stuff that has no benefit to anyone...what if he becomes a crusader for "traditional" family values?  To know if his new state is a net benefit over his old state would require more information.

Religious is not always "bad", but it is rarely optimal.  There are plenty of people who get sucked into secular movements anyway...your story could have been about someone becoming a militant member of PETA.

Edit:  Also, Bob sounds pretty secular anyway.  So the world probably would be a better place if everyone was like him, rather than a fundamentalist fill-in-the-blank.  But in reality, he would do more for the world by leaving the religion alone and focusing on helping real people, just like your examples show him doing anyway.

Well, to be pedantic, you only used (1), not (1) and (2), since they are contradictory, but no matter.  Let's suppose that Bob's Christianity exists in a cultural vacuum, and the only religious concept in the religion is (1).  If Bob believes that man's innate sinful nature demands extra work from him towards making the world better, and then spends his life building houses for the poor, or whatever, and that makes him happy, then yes, I think you've found an example of a uniquely religious belief that would cause good and happiness, on balance.

I'll get back to this example in a minute.

You're supposed to realize that for the most part, uniquely religious beliefs are quite rare.  Most of the things people do in conjunction with their religious faith are not really "religious behaviors."  Going to church, having potlucks, church softball leagues, blood drives, etc, are not religious activities.  They're things that humans everywhere do because they make sense and fulfill basic human needs.

When I criticize religion and faith, I am criticizing exactly one thing and one thing only -- the belief that some things are true despite evidence to the contrary, or no evidence in favor of them.

This brings me back to Bob and his epiphany.  Sometimes, as you know, we can use faulty logic to reach true conclusions.  This is the case with Bob.  Humans are not inherently sinful because sin is a nonsense concept.  Bob believes a false claim about humanity, but follows it to a conclusion that is true -- helping others feels good, and increases happiness in the community.

I've always gone out of my way to make the disclaimer that some people do find happiness in religion, and that religious belief doesn't make people into horrible human beings by default.  I think you've found a good example of a false religious belief that can lead to beneficial behaviors and personal happiness.  You've illustrated very well that false premises can lead to true conclusions.

Have you also considered that this belief does not exist in a vacuum?  Let's pick a denomination that believes in man's sinful nature -- Southern Baptists.  (I was raised SB, so I know all about it.)  Here's what Southern Baptists think is sin, and must be overcome:

1) Pride

2) Lust

3) Lying

4) Drinking

5) Masturbating

6) Sex outside of marriage

7) Nudity

Revealing clothing

9) Dancing (not all SB's believe this, but some do)

10) Associating with sinners (again, not all, but some)

11) Not spreading the word of Jesus at every given opportunity.  (SB's believe that another man's blood is on your hands if you had a chance to witness to him and did not do it.)

12) Cursing

The list could go on for a while.  Trust me, it's like they enjoy inventing new sins.  Anyway, here's the thing -- Southern Baptists believe in black and white morality.  A sin is a sin is a sin.  No matter the reason, if you lie, you're sinning.  If you have pride, you are sinning.  If you lust after a woman you're not married to, you're sinning.  (I never understood how anyone ever figured out who they wanted to marry if they never lusted after anyone, but that's beside the point.)

I picked an extreme example, but I could have gone farther by picking some Holiness denomination or something like that, where they believe women who cut their hair are sinning.  Now, filter Bob's belief through concurrent belief in the Southern Baptist model of sin.  Now, Bob is going to have to spend a great portion of his life feeling guilty for experiencing natural emotions.  He's going to have a moral dilemma when other people would just tell a little white lie to keep everything happy.  He's going to be ashamed of his body, ashamed of masturbating, etc, etc.  He's going to feel guilty because he's too shy to tell everyone he meets about Jesus, or he's going to be the most annoying person in his town because he's brave enough to tell everyone about Jesus.

He'll also do lots of good works for other people, as you demonstrated earlier, but on balance, is he happier than he would be if he had true beliefs about human nature, and didn't believe in the concept of sin?

Of course, this is an extreme example, and I wouldn't hold Bob v2.0 up as an example of all religious people.  Instead, I'm trying to illustrate a basic convergence of principles:

1) Religious beliefs are NECESSARILY not scientific beliefs, and are therefore LESS TRUE than possible.  (Remember, I am isolating religious beliefs as ONLY those beliefs based on faith.  I'm discounting the rare occurrence of blind faith stumbling blindly onto scientific truth.)

2) When the number of religious beliefs increase, the amount of falsehood increases dramatically.

As you can see from Bob v2.0, a religious belief that can produce good results goes horribly wrong when combined with another religious belief.  If Bob only believed (1), sure... religion produces happiness, but it is not the nature of faith based reasoning to stop at one conclusion and then switch to complete rational thinking.  Once we admit that faith is a way to derive truth, we tend to continue "deriving truth" from faith, which will tend to compound our wrongness, which on balance, will increase unhappiness and dysfunction.

Of course, there's a hidden premise here that you're welcome to challenge.  I'm implying that true knowledge tends to produce more happiness than false beliefs.  Sometimes, I wonder if this isn't the entire crux of our disagreements about religion.  But yeah, I think it's pretty easy to demonstrate that humans, being goal oriented, tend to get what they want more as their accurate knowledge increases.  Achieving goals is, I think, the primary way that humans increase happiness.  But that's probably a discussion for another thread.

Do let me know when it's finished.