I was about to say, "Of course they controlled for income, that's totally basic", but I looked. Most of the studies didn't control for class or income. :( Looking elsewhere, income is positively associated with drinking, so income could well be the hidden variable increasing drinking and decreasing mortality.
Also, some of the studies controlled for body mass index, meaning that if your beer gut increases your mortality, that doesn't show up.
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.