It’s like any other kink. There are a few options.
He can give up on it. It doesn’t sound like this is an option for him.
You can participate in it. It doesn’t sound like this is an option for you.
You can decline to participate in it, but allow him to do it with other people. This doesn’t sound like it’s something you’re willing to do.
And you can split up. It sounds like this is where you’re going, and if his interests are in the “it disgusts me” range rather than the “it isn’t my thing, but whatever” range, it’s probably for the best. Also, if you’re asking what “normal” people would do, there’s an implication there that he’s abnormal, and if you really do think that, then he’s probably better off single.