And I agree with both assertions.
I'm a fairly sober person, really. I drink once and a while, usually for special occasions. Gaming isn't one of them. When you drink, drink. When you game, game. Don't mix the two. Why? I've got three reasons.
First, I'd like to break the drunken depressed writer stereotype (Yeah, I know, good luck with that). I ruminate enough as it is. I don't want alcohol to release my inhibitions to speak about religion, philosophy, politics, and "life" at the gaming table.
Second, I'd like to prevent that stereotype from being added to the gamer stereotypes already out there. That is, the "nerdy anti-social satanic overweight smelly gamer" stereotype doesn't need "drunken" and "depressed" added it to it.
Third, in the handul of times drinking and gaming went together, the drinking eventually took precedence--even if there was no alcohol being served. Sure, I've got a few funny stories, but why they are funny is because something sad happened. That's pretty much the definition of comedy.
Sure, there's something funny about "getting too drunk to play D&D," but the end result is that you game to play D&D, but the alcohol took over.
Like the time, years ago, when my DM celebrated his birthday by running a one-shot Dark Sun adventure. While we, the players, had a beer or two, he knocked back some mixed drinks. But at the end of the session he kept forgetting to have the villain take its turn. "Who's turn is it?" he kept saying. And I, who figured out what was going on said, "Mine!" Needless to say, the game had an anticlimatic ending. Afterward, the DM realized that his couch need to be his new best friend.
Even when alcohol isn't being served, it can still have long term consequences.
A campaign of my own ended because a player showed up both late and drunk. A few minutes after he arrived he threw up (fortunately missing the gaming paraphrenalia and the other players). Game over. While the rest of us cleaned up his mess, somebody else took him home. The campaign itself was limping along, but that caused it to fold.
I'm sure some of you out there have got similar stories. While I don't practice it myself, I can understand having a beer or two. It's drinking the hard stuff that causes trouble.
As for gaming and drugs? Never.