How do you phrase that question; why are tw w without saying anything sexist..?
Do you mean how you define the word woman without resorting to sexist stereotypes?
Because it's just that. If transwomen are women, you need to define the word woman in that sentence.
And if it's not adult human female, of or denoting the sex who bear eggs, then what is it?
I don't think you'll have to ask anything more leading than that.
What you generally get in reply is a disagreement about the definition adult human female, due to intersex, and then you lose the will to live and open the wine.
Because they can't actually answer your specific question without being sexist.
The point at which they refuse to answer question is the point at which you know they can't, and you can thankfully leave the conversation (taking what little is left of the wine with you).