The first study talks about the benefits of 12 oz of beer, not 5-6 oz (conversion tables, dude), so it's drinking one beer that aids in the prevention of plaque formation. The second presumes that you know that wine, in moderation, ie 2 glasses for men, has significant health benefits that have been recognized by medicine. thus, in having a comparison between beer and wine and finding that beer not only is as effective in wine in its content of antioxidants, but also greater in its amount of B12, indicates that it, too, has healthy properties. As for the third? Small doses, yes. But they categorize small doses as 8oz serving anywhere from 1-4 times a day. That's close to three beers. As for confounding due to psychological factors, they say that because these factors a hard to adjust for in their analysis because of the difficulty in categorization.
Anyway, I would say that in excess, the consequences of drinking alcohol are dire, but in moderation, it's safe to say that drinking beer has more benefit than risk.