Really there needs to be a widespread campaign by men for men about expanding the bandwidth of being male. So people could be happy wearing what they want, feel OK in male spaces, and not decide they want to invade ours. This isn't a problem created by women, and yet we seem to be the only ones having to deal with the consequences.
Unfortunately that isn't what TRAs want. There is no validation or thrill in men accepting you in your 'women's' (sexist) clothing. They don't want access to women's spaces, they want access to unconsenting women. Upton is a good example of this and the tacit knowledge that this is true is why they bent over backwards to harm Peggie and give Upton all he wanted. He could have been given an alternative changing room, but wasn't (witnesses have said SP could have changed elsewhere - why not Upton?). Because it's not about the changing room, it's about the women. At best for validation, and we all know what the worst is.
If it was anything to do with men not accepting GNC men then third spaces would be everywhere and used by now. But it's not. As evidenced by the fact that these men won't use third spaces even where they exist (as they apparently do at the Vic because SP was told she could change elsewhere though presumably any space she changed in would also be open to Upton - a man determined to bully her).
I also don't think there's any evidence at all that transwomen are unsafe in the mens - many transsexuals use the mens without incident. It's all the most paper thin of excuses for the real goal - which is dominance over and access to unconsenting women.