With a serious head on:
TWAW-type genderists don't consider a male bodied person to be necessarily a "man" . They think "man" and "woman" are types of personalities that have been incorrectly believed to be determined by ones physical sex.
So a "trans woman" in their belief system isn't "a man who is a woman", it's "a person who is a woman but doesn't have the traditionally expected body of a woman".
Real women ("cis" women in genderist language") can mever be trans women because real women have the traditionally expected body of a woman.
If humans had three sexes, male, female and chibble or something, male women and chibble women would both be trans women. (Serious hat slipped a bit with chibble but it illustrates the principle.)
Any GC logic that associates trans women being male-bodied with them being men will fail in genderist terms because they don't see the two as synonymous. To demonstrate the flaws in genderist logic you need to show that it is internally inconsistent.
(Which is it BTW, in so many ways. The most fundamental being "If society was wrong to assume "women" means female, surely all the "women"'s things that were created based on that assunption are the wrong things? So how come TW so desparately want them when they literally reject the whole concept of "woman" that they are based on?")