Your friend's argument goes wrong in about every way that is possible. The most glaringly obvious problem is that he's presenting two propositions that are clearly inconsistent. On one hand he says that right and wrong are determined by the norms of society. On the other hand he insists that we should be tolerant of other cultures. But what if the norms of a society favour intolerance?

When the Nazis invaded Poland in 1939 it was certainly an intolerant act. But what if it was in line with Nazi ideals? A cultural relativist can't criticize the Nazis for being intolerant if all they're doing is following their own moral code.

The cultural differences argument is unsound. It goes from facts about the differences between cultural outlooks to a conclusion about the status of morality. The conclusion doesn't follow from the premise because the premise concerns what people believe,(in other societies people believe something else) but the conclusion concerns what really is the case. Even if the premise is true the conclusion may still be false. It doesn't follow logically from the mere fact that there is a disagreement that there is no objective truth in the matter.

However, there's a much deeper problem with this view. Some social customs are merely arbitrary and it's pointless to say that one way is superior to another. But that doesn't mean that all social practices are arbitrary in the same way. In the case of some practices (like punishing people for what they do consensually in private) there are good reasons to say that one way of doing things is more socially desirable than another. Because we can support our moral judgments on these matters with rational arguments we don't have to regard those judgments as merely expressions of our particular society's moral code.

I don't agree with that at all. To say that the crime is X and the punishment is Y is merely a statement of fact. To go beyond that and say that therefore you deserve to receive that punishment is to make the outrageous claim that there is no such thing as excessive punishment.

Absolutely wrong.

I take it you're a "patriotic" whatever. agreeing to abide by the laws of wherever you live.

Forget Gandhi, MLK, forget Apartheid, forget Henry Thoreau, forget Vietnam, forget Civil Rights, forget Human Rights.

It IS a black and white issue, sometimes it literary is!

In sum, forget you!

There is definitely excessive punishment, but I can't wrap my brain around how to reconcile this with law. If everyone can break a law without fear of punishment, then the law no longer holds any authority. Perhaps, I should be running the logic in reverse, i.e. if the majority agrees that a law is unjust, then the law should not hold any authority in the first place?

I would certainly agree with your post and don't have anything to add that you didn't express.

I disagree.  Too many people are born in a country after the laws are created and without the means to leave, and thus the laws are not always an understanding between a government and its citizens.  This is why free speech is so important.  Only via free speech can laws be criticized and thus changed.  You have to remember that not all countries have free speech, and without it your chances of changing the laws are very, very slim.  Even in America civil rights activists had to break the law by sitting in the wrong part of the bus or restaurant in order to get things fixed.

To OP:  About the cross-dressing/nudity, point out to your friend that "no public nudity" is to protect people from seeing it (right or wrong, that's the justification).  Since this was a consensual act at a private party, the justification applied against public nudity cannot be applied in this case.

Your friend is making the  mistake known as the "is-ought" fallacy.

Notice how freely he interchanges:

"Crossdressing is taboo in Saudi Arabia"

and

"The Saudis did nothing wrong"

Hence he is saying:

"Because it is socially unacceptable to crosdress in Saudi Arabia, crossdressing ought to be socially unacceptable in Saudi Arabia."

Yes, crossdressing is socially unacceptable in Saudi Arabia, but it is possible (and I say it is clear), that the Saudi's are simply wrong about making it a taboo. What is right and what is culturally accepted are sometimes completely different things. I don't care what Sadui's actually do to crossdressers, or what they have done in the past, what they are doing to them is wrong.

Anyone who I've ever talked to who's been there agrees. Even just the odd acquaintance. I had a friend who was working as an architect there, and you never want to ask him about Saudi Arabia. It sends him into an endless tirade.

Why has nobody mentioned that these medeival nomads wouldn't have a pot to piss in if we hadn't found oil under their tents? There IS actually international law, and when we do business with them, they ARE taking part in an international community.

We treat them with kid gloves because they're the drug dealer on the block with the best hook-up. Russia would be the mean drug dealer, and Canada's a total push-over. (The drug would be oil, for those not following.)

We say stuff like, "oh, it's their country, so they can make their own laws" because we don't want to wreck our oil supply. If they were bad trading partners, we'd invade, just like in Iraq. We're complicit in their success as a theocratic feudal state. If they had a democratic state, then the oil prices could very well be out of Western control, and we'd try to mess with their country like we do in Venezuela.

To the OP: that guy you're arguing with is so full of it it's coming out of his ears. Cutting off someone's hands because they stole is ridiculous. Yes, I'm being ethnocentric, and no, I don't care. That's where Osama bin Laden got all his money from, and that whole royal family should have received a huge slap in the face when he organized an attack on US soil.

I disagree.  Again, too many people are born into countries without the means to leave.  They did not subject themselves to the country's rules because it was not their decision to be born there.  Sometimes "begging for trouble" is necessary to fix the laws.  Again see the civil rights movement for examples.

What is right is right, regardless of the person or the nation they are visiting. I will do the right thing no matter what country I am in or what laws I am breaking.

The point I'm trying to make is that it doesn't matter if people plan on "accomplishing" anything, they should do what is right regardless of what country they are in or what laws they are supposed to be following. If the laws aren't ethical,  they shouldn't be followed. By anybody.

Except that I think there is a universal morality, which can be ascertained through philosophy, science, and math (especially game theory).  Laws should be based on this morality, not the other way around.

Murder of other members of your society is bad, and it is bad regardless of what culture you're in.  While some cultures may believe that it is not bad, simple game theory analysis can prove that a group that treats the murder of its own members as good will be far less likely to flourish than a group that treats it as evil.

Historically, mass murders and genocides and such almost always come about after an us-them mentality, when the murderers view the murdered as outsiders, not part of their group.  This is because most people instintively realize what game theory will objectively tell us, that mass killing of your own group is a terrible thing because it will lead to the destruction of your group.  These people can only justify mass killings by drawing new group boundaries.

There's plenty of evidence and reasoning out there that can lead to objective morals.  Just look at history.  Figure out what made the flourishing societies flourish and that's a good start at defining "right."  Figure out what made the failing societies fail and that's a good start at defining "wrong."  Mix in some game theory and some science and you've got youself an objective system.

But I never said murder was inherently wrong.  I said that murder of other members of your group is wrong.

Oddly enough I just wrote a facebook note about this stuff.  Here's the basic idea

Whether or not action X is moral depends on some of the circumstances in which action X is performed

However, action X performed in circumstances C is objectively moral or immoral

The idea is that the morality of a given action in a vacuum can't be determined, but the morality of a given action in a specific set of circumstances can.  The morality of actions are relative to circumstances but the morality of action + circumstances is objective.

So I don't claim that murder in and of itself is wrong.  I claim that murder in the circumstances that the victim is part of your own group and that you were not doing it in defense of yourself or another is wrong, and that it is wrong regardless of whether or not you think it's wrong.  The evidence for this comes historically and from game theory.

In the natural world, there can be nothing that "ought" to be. There is no "should;" there simply "is." Thus, to me, morality is an entirely human concept, so you can never say something is absolutely right or wrong.

Let's say, for instance, murdering children for fun is wrong. I'm sure we can all agree on this. But, why is it wrong, because harming others without justifiable reason is wrong? Well, why is that wrong? I mean, don't you still begin with some assumptions about what is right or wrong? It seems like, with objective morality, at some point, you'll always need some rather arbitrary axiomatic(?) criterion. Ultimately, a thing will be wrong for no other reason than that we feel it is wrong or, with most theists, God says it's wrong.

A version of utilitarianism? 

Don't you still assume that the highest overall payoff "ought to be?"

Vastet you missed the point of my second statement.

Person P finds action X morally objectionable.

This is an objective statement even if the statement "action X is morally objectionable" is subjective.  The fact that Person Y, animal C, and plant G don't think about action X in the same way as person P doesn't change the fact that Person P finds action X morally objectionable.  The statement's truth doesn't depend on who's reading or analyzing the statement.

Also, I never said that defense is good.  Just because I don't claim it to be always bad doesn't mean I claim it to be good.  I haven't made any claim about defense.  Although perhaps I should add "for the group" to the end of that statement.  Also, if value is subjective then we just have to provide a reference frame to make our claims objective.  The basic idea is this:

Statement S is subjective

The statement "Person P believes statement S" is objective.

The idea is that even if some moral statements are subjective, this does not mean that all moral statements are subjective.  Same with values.  We just have to define a reference frame for the values.  Living beings want to live and often meet other living beings whom they want to live.  Thus they assign a positive value to life.

You're confusing absolute with objective.  I never claimed morality was absolute, I only claimed that it was objective.

Absolute: If person P performing action X is right, then person Y performing action X is also right

Objective:  If person P performing action X is right, then the truth of the statement "person P performing action X is right" does not depend on who reads the statement.

Notice that objective has nothing to do with actions being moral for everyone.  It just means that the morality of a person performing an action doesn't depend on who's answering the question "is it moral for this person to perform this action."

Butterbattle, X yields better results than Y.  This is all one really needs for a practical system of ethics.  I don't think we need to have any talk about how things ought to be.  Just knowing that if you want good results then action X is your best bet is enough.

Also, I see what you mean about there needing to be some beginning, some sort of intrinsically good thing.  My system generally rests on "Things that we desire to have are good.  Things that we desire to not have are bad."  From there we can derive a lot of other morals that maximize expected desire fulfillment while minimizing expected anti-desire fulfillment.  But even if we want to take different starting axioms the method proposed is still objective.  All moral statements will just amount to "if these axiomatic moralities are true, then these derived moralities are true," and getting people to agree on a small set of very basic axiomatic moralities will be a much easier task.

Okay. 

"So wait, would the act of P having brown hair not be objective because P must exist and have vision and linguistic bias to claim to have brown hair rather than dirty blond?"

Completely different scenario. Hair colour is due to refraction of light, which always refracts the same way. Morality requires perspective to exist, and can vary wildly. Brown is brown whether there's anyone to observe it or not.

The whole point is that there must be a living being involved for morality to exist in ANY scenario. Due to the selfish and emotional nature of morality in the first place, it is impossible for any morality to be objective. It MUST be subjective, by definition.