I agree that there's some merit to treating alcohol's effects on you and others separately, but if we do that, shouldn't we then also work to exclude some of its benefits as "social externalities"? Like the whole "alcohol -> socializing -> mental well-being"-pattern?
You should exclude the mental well-being of the others you socialize with while drunk, yes. But that's not going to show up on your personal longevity.
My roommate recently sent me a review article that LW might find interesting:
Personal observation says that LWers tend not to drink very much or often. Perhaps that should change, to the degree suggested by the article?
Full article here.