what that dude appears to be implying is that it's ok for a male to swing his dick and balls in a naked female only spa SO LONG as he has a particular mental state, which is that he identifies as or believes himself to be female.
That's exactly it, yep. The defense is that it is okay for a person to behave in any way they please so long as they have this undefinable, invisible, unmeasurable mental state.
In fact, they don't even need to declare this mental state - it's inferred by their actions.
What wokebro is saying is 'if there is a male-bodied person in the female space, then by definition they are [probably] a transwoman' (and the woman is 'being a dick' for asking the question/mentioning the fact).
It's as if voyeurism or fetishism has been erased as a thing, as if it never happened and could never happen. The possibility of a person in the changing room being there for sexual gratification is something that we are not even allowed to suggest or ask or infer. In case it might upset a person who is transgender.
I think this is enormously insulting to transgender/transexual people, in fact.
I remember the male in the woman's shelter with an erection and how they were defended by the staff of the shelter. The argument is that we can't presume someone has sexual motives, but I still can't actually see what behaviour they would consider proof of unacceptable motives.
We don't even get to the point where we can question the transgender status of this person. If they are there, no matter what it is they are doing, then they 'might' be transgender, and are therefore exempt from questioning/comment.
I am not sure, at this point, where this dudebro would draw the line. Is there a line for him? What behaviour does he deem unacceptable? Is there anyone or anything that would be barred from the woman's space? It sounds like he is saying that woman are to accept anyone and everyone in the woman's space without ever, ever voicing any discomfort or concern.