This same argument could be made against any other minority (or majority) group: Jews, Muslims, women, disabled people, and so on. None of them are forced into the community either. Surely it wouldn’t be a problem if they could be openly mocked for those qualities, right?

I personally don't think it's a good idea to alienate any of those groups, including trans people. Banning assholes is a great idea though, regardless of what their identity group is.

But I don't think I have any right to tell a project what they find acceptable or not. Like I said, it's not like everybody has to participate, and there are plenty of projects with different rules and vibes.