@Nullo
The problem words here are “similar” and “delusion”, the latter of which is plainly presumption.
Your examples are not similar. Someone suffering from the delusion that she is a porcupine will look in the mirror and “see” a porcupine. More importantly, such a delusion interferes with daily life, contaminates one’s human sense of self.
But someone suffering from gender confusion, or someone who has adopted an alternative gender, looks in the mirror and still sees clearly, without delusion, that she possesses breasts, a vagina. She simply feels that her sex (q.v. breasts / vagina) is not perfectly representative of her gender, which is to say that gender is an internal state, a feeling, and something that develops with a relationship to sex but is not shackled to it. But until she begins to see a penis when she looks at her pelvis, it is not a matter of delusion.
This discrepancy between gender and sex, while challenging / confusing / frightening to those who experience it (and apparently to others like you) is for the most part innocuous and becomes a necessary part of a person’s identity—a person’s human identity. There is nothing harmful or classifiably unhinging about the phenomenon; and by the same token few could deny that the more harmful event is actually the reinforcement of strict gender roles.
As far as I can tell gender is like a feeling or a sensation in somebody. You would not tell someone who feels angry that he is delusional, that he cannot be angry, cannot be feeling anger when he knows he is. Of course, gender is not quite the same as emotion, but his experience with his anger, as well as with his gender, is often something he cannot avoid.
I find it ridiculous that you are able to dismiss this as a delusion, the same kind of mental malfunction to which homosexuality was once relegated in the popular mind of psychologists and “literally billions of people” at various junctures of human history.