I'd say he doesn't deserve the former, and he has probably already heard the latter (so it wouldn't make much of a dent).

Do you have anything more severe you can say- something he'd remember, which would keep him up at night?

If you really wanted to, you could give him a proper Hannibal Lecture: http://tvtropes.org/pmwiki/pmwiki.php/Main/HannibalLecture  And completely demolish his ego.

I don't know much about him, but this might work- If you feel like he needs to be told something:

Maybe tell him that he knew drinking inhibits judgment- this is well known; it is for a sober person to choose not to put his or her self in such a situation where such inhibited judgment could be a problem.  Neglect to do so is equivalent to the choice to kill people- a significantly probable outcome.  It's like giving a baby a loaded gun to play with and then claiming innocence when it goes off.

Tell him that anybody who gets drunk in a situation where they will need to drive somewhere, and does so without a designated driver to stop them from making a bad decision, has chosen to drive drunk through that negligence- and has *chosen* to kill the people he or she killed.  That here, he has chosen this.

Tell him he brought that upon himself with his own choices- it wasn't any kind of accident, it was apathy.  He didn't care enough about his friends to give their lives that simple consideration when he chose to become drunk in that situation.

Tell him you know everybody else is asking him what he was thinking- but you won't ask that, because you already know. 

Tell him he knew the risks of something bad happening when he decided to get hammered.  He was thinking his irresponsible kicks for the evening were worth risking human life- something he held in so little regard to even take some very basic but marginally inconvenient measures to protect- that's what he was thinking.  His amusement and convenience was worth more to him than safeguarding the lives of those who depend on his behavior- that's what he was thinking.

Tell him he chose this- he can't pass it off as an accident, or a product of simple ignorance.  Deny him that coping mechanism- deny him the lie of distance from his actions- make him own them.

Tell him all of that, and tell him that it should have been him that died in that crash- hell him if he were any kind of human being that he would know that already. 

Tell him that he has so little regard for the lives of others that, no matter what the courts decide, he should know damn well that his very existence is a threat to those he pretends to love.  He can't stop drinking- no, that would ruin a good time- and even if he tried to stop drinking, he's an alcoholic and he's too weak and lazy not to cave to pressure and addiction.  And when he does, he'll be too weak and lazy to bother taking measures to ensure the safety of those around him- just like the last time- tell him he's a creature of habit, and he'll just do it again and again until he's locked away forever or kills himself- ask him how many people he wants to kill before that happens.  What's a couple more?  He's already chosen to be a murderer by gratifying his own selfish gluttony and sloth and scoffing the responsibility to society- what's a couple more?  How about some children to add to his tally?

*Maybe* even tell him if, deep down inside somewhere, he really did care about anybody other than himself- about anything else beyond his jollies- that he'd kill himself right now before his own selfish and pathetic nature got the better of him again and resulted in more people getting hurt or killed.

In the last case, though, only do that if you're ready for the possibility of him going through with it, and you would have to be mindful of potential (though unlikely) criminal liability.  It *should* fall under free speech, but if he actually did it, then you could be culpable.

Laws vary by country, and even by state:

http://euthanasia.procon.org/view.resource.php?resourceID=000132

Without prescribing a method, or explicitly assisting the process of suicide by explaining how to do it, it's profoundly unlikely that you'd be found liable, though. (like being struck by lightning unlikely)  Particularly because, in the perspective of most likely juries, he had that kind of thing coming- and while it does presume a bit, not a word of it is demonstrably untrue. 

*disclaimer* In any case, I'm not your lawyer, and none of that is formal legal advice, so talk to a lawyer first if you want to tell him he should off himself.

Philosophy, however, I can touch on:The rightness or wrongness of it depends on how you view the answer to that pesky moral question: 

Do you try to push the alcoholic who habitually choses to drive drunk risking the lives of others (and will almost undoubtedly do so again) over the edge- a man whose life by most rights is already forfeit- to save potentially many others from a repeat offense?  Or just let things be?  What if there are pedestrians next time?  What if there are children involved?

The moral perspective is, of course, highly subjective.

Personally, I tend to come down on the side of capital punishment where guilt is not even remotely in doubt, given even the slightest chance of a repeat offense- and drunk driving has more than a slight chance (taking away the license doesn't do much, and even mandating cessation of drinking is rarely effective at actually curing an alcoholic).  If the courts won't hand that down (and they shouldn't if there's not enough proof), I don't see anything wrong with encouraging the person's own conscience to do justice.

But that's just me- some people have visions of gumdrops, lollipops, unicorns and second chances.  People are within their rights to be optimists if they dislike reality that much- not saying that's a good thing though.

As to the slogan, though, I would advise that the suggestion must not be "Don't drive drunk", because a drunk person isn't the one in the situation to make the choice- rather the suggestion should be "don't become drunk in a situation where you will need transportation without a designated responsible sober adult there committed to providing it"

(Can you tell I'm not very fond of drunk driving?)