Transmen are my sisters, and I welcome every woman that has detransitioned, or reidentified, or just realised that she is female and always will be.
I think that women that have been masculinised through testosterone use, and possibly through cosmetic surgery, have some really difficult decisions to make, regarding which changing room to use. Their response to this is going to depend on many things, including any ongoing presentation differences (is she keeping her facial hair? Does her body now more closely resemble a male body, in terms of secondary sexual characteristics?) We don’t prevent women that have had double mastectomy from using women’s changing rooms, so surgical changes aren’t the defining factor.
They are at risk in the men’s facilities, and if the men realise that they are female, they can be raped, risking pregnancy and lifelong implications. If they use female changing rooms, they can terrify women using those changing rooms, who may assume they are men.
If re-identified women are likely to be able to use the women’s changing room without alarming other women, then there is no issue. That’s where they can go. It’s more complex for the medicalised/surgically changed women.
I believe we are going to have to ensure that third-space provision is available. Whether that’s a ‘unisex’ space, an individual cubicle, or in extremis, the Accessible Toilet.
This is the only way I can see us providing a space that is safe for every woman, including ones with masculinised secondary sexual characteristics.