Hang on it wasn't Delusions of Gender I was thinking of (though I also think it's a brilliant book) but "The Equality Illusion" by Cat Banyard. That's the angry-making but amazing one.
I think my "peak trans" moment, if you like, and I get that is a bit of a loaded term, but it was a throwaway comment by a transwoman that if she was walking alone at night and was ever threatened she would deepen her voice and revert to her previous, more masculine walking style and basically use her male body to intimidate her attacker and get herself out of the situation.
It just kind of made me crumple a bit. It's not the same situation as a woman who is very physically fit fighting off an attacker with self-defence techniques. It's not even the same situation as a physically slight man fearing assault. It's literally turning around and saying "Don't attack me. I'm not who you want. I'm not a woman really." It reminded me (yet again) that it is different to be female in our world and it's not something you can just turn on and off like an identity.
We don't choose this but we are oppressed for it. Femaleness is not an identity. It's not a burden or a blessing either, it just is. And we are treated differently because of it. It is 2016 and sexism is still sickeningly everywhere and mostly invisible. A lot of it is arbitrary but actually most of it is not and it can be traced down to a root of women being the child-carrying class. Regardless of whether we are fertile that is where it comes from. Patriarchy seeks to control women's sexuality because of the fear that we might become pregnant with the wrong man's child. Of course this is so far back in the depths of time that it seems ludicrous but you follow every sexist thing back and it comes down to either women being "destined" for the caring work which is not valued by our capitalist, patriarchial culture or it's about controlling women's sexuality and making it only on mens' terms. Honestly. Try it. (I probably sound insane.)
I don't have any problem with transgender ideology in theory. I am perfectly happy to use whatever pronouns somebody wants as long as I remember (I'm a bit forgetful). I don't care what people want to wear or do with their lives, subvert expectations. Great! I love the idea of anyone living any way they like as long as it doesn't hurt anybody else. I don't even mind particularly about some argument about toilets. Give me a cubicle and I'm happy enough. Most people, after all, are just trying to use the toilet.
Where I stumble is when I remember that women are oppressed and still need space away from the oppression of men. That doesn't stop me sharing my house with one but it does make me believe that sex-segregated space is still necessary. And why is it necessary? For no reason to do with gender, only sex. Which means that gender has absolutely no basis in a discussion about which sex-segregated space somebody has access to. Ask yourself why something is split and whether it is still necessary. Sometimes it is silly or outdated but sadly, in many situations it is necessary to split people by their sex. It's absolutely nothing to do with excluding people or making them feel less accepted. I'm perfectly happy to accept someone as who they say they are even if it's a bit confusing. On the other hand, there is no need to bend rules which exist for good reason in order to do that.