What if his religion forbade the use of religious iconography, including such things as demons and devils, or forbade pretending to cast spells? Would it be reasonable for him to expect gamers to forbear?
Sure - we'd be playing Champions (or M&M or....)
If that was a restriction, I wouldn't be looking for a group that gamed fantasy. I have never said drinking is bad - just that I won't be in a group that has it. Generally that means that I will leave a group because that attitude (as has been shown by this thread) is uncommon, and oft misunderstood. I'll live without a group that engages in something I prefer to avoid.
It isn't a "take my ball and go home" thing - it's "drinking of any sort makes me uncomfortable enough that I would never feel comfortable in a group with drinkers, so I leave so as not to disrupt anyone else's fun".
With the thought experiment you describe it would be the same thing - if that sort of thing made me uncomfortable (or was forbidden as it were), then I would just find a group where that difficulty doesn't come up - as in my flip answer of playing a superhero RPG where that sort of stuff doesn't come up much (if at all).
It isn't, to me, asking someone to forebear - it's a clash of game styles. If my presence was seen as necessary for the group, and the group needed me there, I would explain my position about alcohol, and ask people not to drink while I was around. If that wasn't possible I'd leave... so that those that wish to drink still can.
It's all about the social dynamics of the group.
