Playing games while drinking does lead to some interesting discussions. First, the very notion of just what drinking is varies from person to person. To one guy, drinking just means he's sipping at a beer or two while he's running instances or shooting people in the face. To another, drinking is really the primary behavior, and the gaming is just secondary. The former situation happens all the time, and likely isn't even noticeable to the others participating, while the second perhaps occurs a bit less frequently and is impossible to ignore if you're trying to game with the drunkard.
I don't concern myself in the slightest with people who choose to get smashed and play a game with themselves, but I take serious exception if they're in a position to impact my enjoyment of a game and waste my time. Whether they're team-killing and being ineffectual in Counterstrke, or worse, part of a WoW raid that I'm in, what they're doing is more akin to the obnoxiousness of someone roaring drunk in public.