Would you refuse to go to a concert if the guy checking IDs had a large Bible verse on his shirt?

[100% pro-life no matter what]

Maybe I don't go to enough concerts, but the "guy checking IDs" part is the one that caught my attention the most.

Every one in the US in a venue that serves alcohol does this. How else do they confirm if you're old enough to drink?

I would think you get checked at the alcohol booth or bar stand (depending on what "venue" means here), but I guess not.

I'd say that it depends on the size of the venue.  More mainstream music acts playing in stadiums, arenas, or major concert venues wouldn't have someone checking IDs at the door.  Likewise, live music in a restaurant wouldn't have it either.  More club-like venues (or some bars at night, particularly in cities) would have someone checking IDs at the door.

I'd probably be less likely to go to a concert venue with ID checking at the door because it's less likely to be my scene.  Maybe once every year or two, I'll go to Broadway with friends, but it's not really my favorite as a non-drinker.