On a post about Great Britains sex-based spaces laws that was painted as trans people being “banned” from public restrooms, I pointed out that they are not banned, they just have to use the ones that are for their sex.

Nothing incorrect there. 100% factually correct. Sex and gender are constantly spoken about as being separate things now, since sex is not changeable (despite what the person who replied thinks)
I was then permanently banned for “transphobia”:

Do they even understand what a phobia is?

Almost no one in regular usage considers female or male as sexes separate from ‘woman’ or ‘man’ as genders in social situations; defining transgender people in that way is largely equating them with crossdressers.
If anything, those calling for bathroom bans are trying to erase the notion of gender as being separate from sex entirely as they by and large believe transgender women are men (and transgender men women), even if you don’t.
Ultimately, both positions deny transgender individuals equal status with the cisgender individuals they share a gender identity with, and are therefore both transphobic. It’s not possible to push for a bathroom ban without being transphobic.
Ultimately, sometimes it’s best just to agree to disagree.