What they see as “bad research” is looking at an older cohort without taking into consideration their earlier drinking habits - that is, were they previously alcoholics or did they generally have other problems with their health?
If you don’t correct for these things, you might find that people who are not drinking seems less healthy than people who are. BUT, that’s not because they’re not drinking, it’s just because of their preexisting conditions. Their peers who are drinking a little bit tend to not have these preexisting conditions (on average)