Correlation does not imply causation and such. For the latter to be tested for, a randomized study that makes people change their drinking habits would be required. The hard part is blinding it, of course.
I don't think that the kind of people who are willing and able to take part in a randomized study of alcohol consumption are representative of the general population.
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.