Scientific American's departing editor and the politicization of science

It's quite informative to read the forums where trans-identifying people discuss this, to see how these false beliefs develop. One can observe the trajectory of, say, a male who wants to be a woman. He'll start out with desire to be a woman, move onto the idea that he "feels like a woman" despite having no insight whatsoever into what being embodied as female is actually like, and then slowly, within the echo chamber of like-minded males, he'll start to believe he actually is a woman.

Sometimes this will be through believing he has a "female brain" in a male body. Or perhaps he might think he's "born in the wrong body". Or maybe he'll start to believe that being a woman or a man is based on some internal "gender identity" of which he has the female type. Sometimes this is given a spiritual aspect, like a female soul.

If he takes drugs to suppress testosterone and boost estrogen, he may start to believe that he is no longer of the male sex but is becoming female. Even more so if he elects to have surgery to remove his testicles and fashion his penis and scrotum into a non-functional cosmetic simulacrum of the female external sex organs. Some of these males even start to believe they're having a menstrual cycle, despite lacking any anatomy involved in this process.

However he reaches these conclusions about himself, every single one of these beliefs is false. These are delusions.

Your argument builds upon two assumptions: 1. There is a finite number of pre-defined gender-identities which are not interchangeable. 2. Identity is bound to biological organs

I see no proof of these assumptions. How humans see each other and themselves is not primarily chosen by their unchangeable (save medical interventions) organs but by how we are read by our peers. We are not talking about a purely biological problem, but a social one. Humanity has, for the longest time being, assigned fixed profiles to these readings, which luckily has started to break up in the last decades. Now of course each individual is free to base parts of their own identity on their unchangeable biological traits, and you also are free to do so, but that does no generalize to the whole population. Humans should be free to base their identity to their own liking.

This can lead to some cases which do not make sense like your "male menstrual cycle" example, granted. These anecdotes however as well do not generalize towards the initial claim of the other user and the first assumption.