I think that this issue is one of those that shows that we've come to the 'end of feminism', in a crucial sense. The whole thrust of feminism, for over a century, has been that women could do what men do. That's been entirely correct, in my view: the strength of humans, relative to other species, is all about humans' mental capacities. Never about their physical capacities. Relative to chimps, horses or even tigers, the difference between men and women is tiny. Humans' strength is in their brains. And there's sod all difference between men and women in that respect - if any at all.
The GC argument is anti-feminist. It wants to assert that women are inherently inferior to men in ways that are still in some way important. It also wants to assert that women are, in various ways, nicer than men, in some crucial respects. This is why GC advocates are fine with any kind of natal woman in a woman's bathroom - because women are unfailingly lovely and fluffy - whereas any self-identifying woman, no matter how small and fragile she is - if she has a penis and testicles, or even once had a penis and testicles, is, ipso facto, a menace to all the women around her.
Sport is sport. Whatever. A tiny percentage of women will ever be involved in it to any great standard. The tiniest of tiniest percentages of transwomen will ever be involved in it at that level ... the fingers of one hand, maybe.
Gah ... of all the things we women have to face, the issue of transwomen is so, so tiny. I really do think we should move on from it. It makes us look silly, tiny and weak that we're so scared of people who were born equipped with penises and testicles. We are better than this ridiculous argument.