The problem is simply that a boy pretending to be a girl and playing on the girls team is cheating.

It doesn't really matter what the excuse is. I might be sympathetic to some confused kid that really thinks he is actually a girl in the same way I think we should be sympathetic towards anyone struggling with mental illness. But at the point where they begin to demand that they be allowed to essentially cheat and ruin the game for everyone you can't really let them in. You don't know if they are pretending to be a girl to win or if they are actually crazy. But it doesn't matter.

What if someone who didn't have a disability wanted to play on the disabled team. What if a professional baseball player identified as a little leaguer and went to dominate the world of children's baseball.

There are open sports leagues out there and plenty of places where mixed groups of men and women are allowed to play together. I'm sure that gay people are welcoming if they are gonna make a gay sports group or whatever as they seem keen to make gay groups about hobbies where being gay is irrelevant. There's simply no compelling reason to allow men to play on the women's team. "It hurts their feelings to be excluded" well tough shit it hurts my feelings to be excluded from the presidency of your organization, what you gonna do about it? Keep up with your bullshit gatekeeping? I said I wanna be in charge and you aren't letting me be in charge, that's genocide silly.