"Once gendered behavior has been determined, however that occurs, cisgender males don't say "I'm a boy!" for cognitive reasons that are substantially different from the reasons that transgender males say "I'm a boy!"

Except "cisgender" boys don't generally engage in questioning "am I really a boy".

Those people are called "cis", because traditionally when an opposite of "trans" is needed "cis" is it.

You know, we don't have a word for people who aren't schizophrenics or say don't believe they are avatars of a god either.

• If someone cares strongly about whether they're regarded as male, female, or something else, then in the absence of strong special reasons for doing otherwise we should go along with that preference.

  • If, for instance, they take on the considerable social cost of telling everyone that they want to be known by a new name, addressed with non-standard pronouns, etc., that is good evidence that they care strongly.

Except we don't, and can't, apply that logic in any other situation, otherwise we'd find ourselves going out of our way to accommodate every nutcase and everyone who finds it convenient to pretend to be a nutcase.

• If someone who appears (say) male by all other usual criteria says they're "really" a woman, I don't think "believe" is the right word for what I do in response, although "disbelieve" would be much worse. Rather, I don't think this is the sort of thing there's some kind of objective fact of the matter about; we get to choose how we classify people, and I'm happy to do that classifying -- for most purposes -- in ways that are strongly influenced by people's expressed gender identity.

What about someone who insists that Jesus talked to him? Or the classic reductio ad absurdum of someone who insists he (or it?) is an attack helicopter?

Like I said in the parent. I'm not taking orders from a glorified janitor in the middle of an emotional meltdown.