I totally agree.
But I'm thinking in terms of the kinds of arguments that might penetrate the skulls of the fence sitters and the be kind brigade.
For example, my best friend, who I love and respect very much, would tell you if asked that trans women are women. If you asked her to explain why she believes they are women she would get flustered and upset and say she didn't want to talk about it.
We don't talk about this subject very often because she doesn't want to, and I don't want to lose her friendship. We both know that we are diametrically opposed on this subject.
I know that she is coming from a place of wanting to be kind, and is also undoubtedly influenced by her social circle (London based, university educated, Labour voting 30 something professionals working in the public and third sector, where it would be social and professional suicide to say that a trans woman is a man).
When we had a debate about toilets and changing rooms, she said she thought people should be able to use the facilities where they feel safe and comfortable, and I said, "What about the women who don't feel safe or comfortable sharing these spaces with members of the opposite sex? What should they do?" and she had no answer.
I know that if we were to have this conversation again and I said, "I don't want to share toilets and changing rooms with trans women because it makes me feel uncomfortable" she would think I was being mean and probably say something about how trans women are the most vulnerable people in society. If I pointed out that some of them are literally convicted sex offenders she would get very cross and the conversation would have to end there because we would be on the point of falling out.
But if, instead of saying that I don't want to share toilets and changing rooms with trans women because it makes me feel uncomfortable, I said that many women who have been raped can't share toilets and changing rooms with trans women because the presence of a male bodied person is going to set off all their trauma responses, and that those women have a right to feel safe and comfortable using toilets and changing rooms too, she wouldn't have a response to that. Because she would know that I was right. She might not come out and say, "Yes, you're right, I didn’t think about it that way but of course including trans women in women's spaces is going to result in vulnerable women being excluded", but she would at least privately be thinking, "Oh shit. Are we the baddies?"