No, a fact. Gender is distinct from but related to biological sex. If you can't grasp this very simple fact, you don't need to be participating in this discussion.
Says who and why? Be real specific.
So it's black and white, except where it isn't. Brilliant.
This is just transphobic garbage that barely merits a response, but here goes - in 1780, the height of manliness included silk stockings, wigs, makeup, and ruffles. That has changed in the last 240 plus years despite, to my knowledge, the biology not changing at all since that time. Because gender, an outward expression of characteristics associated with biology, is not the same thing as biology.
There's no reason that a man can't be born female and grow to be a man - and a substantially better man than any goddamn transphobic piece of trash.