This is my line.
Will including this person tacitly exclude any women from female single-sex spaces intended for women?
I've thought about it and I've thought about it, and I couldn't come up with any reason why we should care more about a space being inclusive to transwomen than that it should be inclusive to women, that didn't break down to my own internalised misogyny.
We've all heard about how important toilet access is to trans people I think. Well, of course it is. They're human beings. Toilet access is important for people's health, comfort and dignity.
The first problem is that women are also human beings. If any women don't feel safe when using public toilets, it has just as big an impact on their lives as it does the trans people.
So we've shifted the problem somewhere else, instead of creating facilities for the group who needed them.
The second problem is, it's not just about toilets. It's about things like single-sex hospital wards. I do not want women feeling uncomfortable and unsafe in hospital, because someone that looks like a man to them is in the next bed. I don't want sick women self-discharging from hospital because they felt unsafe.
If one woman says no, it shouldn't matter if 99 say yes. If her no doesn't matter, then we're saying that transwomen have more right to decide who goes in women's spaces than a woman does, if the woman gives the incorrect answer.
It's like a shared house. Suppose Dave wants to move into your house and 5 out of 6 people say yes. But the sixth, Peter, says no.
Does Dave's wish to move into the house really trump Peter's? It's Peter's house! Being kind to Dave and letting him move in necessitates being extremely unkind to Peter.