But beyond and aside from that, I will never understand why we have to act like sports are some sacred thing whose purity must be protected. It’s people playing with a ball.

Because you're not thinking big enough. The "trans sports" debate is literally just bigotry. Seriously, go watch the John Oliver piece on it. Every study that has ever been done has found that any advantage trans women and girls have disappears after a few years of hormone therapy. The athletic performance of trans women is well within the range of that of cis women. Believing trans women should be banned from women's sports because they have an unfair advantage has no more scientific validity to it than the old racist beliefs that black athletes couldn't compete fairly in white leagues. The science has been. The studies have been performed. Cis people just refuse to believe them. Their gut feelings outweigh science and our humanity.

People just vote based on bigotry. Even most liberal "allies" are awful at this. Most liberal allies just see trans women as drag queens, literal men in dresses, as if we don't take medications that completely reshape our bodies on a biochemical level. Morons, even many moronic Democrats, just think "trans woman == man in dress," and conclude that our sports performance must be closer to cis men than cis women. It's just stereotypes and bigotry. That's all this is.

And that's the problem. Because once you've given into one form of irrational, unscientific bigotry, you have no reason to ever stop. If you won't listen to the science when bigots say trans women have an unfair advantage in sports, you won't listen to science when bigots say that trans women are a threat in women's restrooms and locker rooms. If you don't give a shit about science, you'll have no problem caving to bigots who hand wring about trans kids receiving trans healthcare. It's completely unscientific and bigoted to let a tiny minuscule regret rate influence your conclusion, but if you've abandoned science once, you'll do it again.

As a trans person, I honestly do not give two shits about sports. But what I DO care about is the precedent it sets. There has never been a state that passed a trans sports ban through its legislature that then didn't also go on to persecute trans people in numerous areas of life.

Think more than two seconds into the future.

Remember, Jim Crow was passed because white women didn't "feel comfortable" sharing spaces with black women.