You can't discuss anything with a group of people who are often wrong, but never in doubt.

"Men can't get pregnant"
"Source?"

Depends the definition of men you’re using. Gender roles themselves are both empirically and historically obvious social constructs, and biological gender is two: neurological and sex-based. Ones sex doesn’t necessarily match with the brain, nor one’s personal perception of their gender or self. If we’re referring to men in a sex-based manner, then no, they usually can’t get pregnant (exceptions in biology exist, especially at the chromosomal level). If viewing it through a neurological lens, then yes, men can get pregnant. Not too complicated.

If being a man doesn't mean something clear, then it doesn't mean anything. Just because you think you are a man but you are not does not make you a man in any way.

It’s very clear on the physiological side, most of the time at least. Thinking is different than being, and sex is different than gender. Gender is what’s in your head, and it usually matches with your sex, but not always, which isn’t a disorder based on the fact that the only working treatment is to affirm their gender.