This is an amazingly comprehensive and effective dismantling of Stock's line of argumentation.

I am curious, though: do you actually view the claim that trans women are women as completely a moral assertion, merely an expression of solidarity? If yes, do you further hold that except in matters of survival and similarly critical issues, we generally leave whom to express solidarity with up to the individual?

Because if it's actually just solidarity, a completely logical reply could be: "no, trans women don't, typically, have the qualities with which I intend to express solidarity, so I will not call them women". And the answer would have to be along the lines of: well, I choose otherwise, but you do you.

Most people, instead of taking the direction you do--which I think is spectacular at refuting Stock--tend to try for an argument about societal deference to internal mental states.