One more thing: if the person you are talking to is reluctant to engage then I wouldn't recommend doing this all in one go.
But if you have a conversation one time about prisons, then rape crisis centres, then maybe next time you mention sports, unless the person is really completely blinkered you will eventually get them to a position where they say that trans women should be treated as women except in certain limited circumstances, such as the ones we have talked about.
If you're really feeling lucky (punk), you can then say, "Well if you don't think trans women should be in women's prisons/rape crisis groups/sports then you don't actually think they are women, do you? You're just saying you do because you think it's important to be kind. But in doing so you end up being unkind to other groups who are negatively affected by this."
That one is a bit of a punch to the gut and might backfire though. It's a doozy if you want to "win" the argument but less good for actually winning hearts and minds.
A gentler approach would be to say, "OK, so if trans women should be treated as women except in certain situations like the ones we talked about before, what does that actually mean? What other situations are there where society actually segregates men from women, and why? Because if it's just about using preferred pronouns and respecting people's right to present as they wish, a lot more people would be on board with that if they knew their own rights and safety had also been taken into consideration."
And then at some point, if you succeed in getting them to acknowledge that trans women shouldn't always be treated as women, you can point out that according to trans activists they would be TERFs, and women are bullied on and offline every day by trans activists for saying exactly the same things they have just said.