But if you know it will be awkward, why go through it?

This is manipulative. It wont be awkward if he doesn't make it that way; he's the only one with an issue, and the issue he has isn't real. I suppose you could take this as a heads up that he will be making things awkward if you don't do what he wants.

I see many red flags here. I think it's super weird he wants you to call people out of the blue, and ban them from public venues just because you'll be there. What is this, high school? He should be even more mature than you given the age difference, not less. Most adults realize that you can be in a room with people you don't like without interacting with them. You've mentioned this yourself, with the example you give about bands who tolerate your presence despite personal issues. You are correct about this being the way adults address situations where they're in mixed groups of people.

I think his request is super weird, and I feel like it's also pretty manipulative that he says "its your call" but then continues bringing it up, obviously trying to convince you otherwise. That's not respecting your decision or judgment at all. Is he just going to keep talking about it until you agree with him? How many times will you have to repeat yourself for him to accept your answer? He's already got you doubting yourself about this, judging by this post.

My money would be on there always being SOMEONE he has an issue with, and if you comply with this, what will it mean for the future? Who will he have a problem with next? Will you have to cut the next person out too?

There's a reason that older people date younger people, and it's often a lot to do with control. I don't disapprove of may/December romance per-say, but it is a situation in which everyone must tred that much more carefully. So be careful, alert, and call bullshit when you smell it.