what's insulting about the word CIS? It literally means person who identifies as the gender that they were assigned at birth.
I just wanted to revisit this.
There is a fundamental difference between sex and gender. One that has been muddied by an inability to say 'sex' and by people with an agenda.
SEX is observed at birth. XX or XY, vagina or penis. Which means might you have eggs or ejaculate sperm? Basic biology of not just humans, but any animals that sexually reproduces. You cannot pretend that doesn't exist. It is the only reason the human race exists. Dog breeders don't put any two dogs together and say, "who knows if they will breed?" if they both have the same plumbing.
Partially as a result of SEX differences, gender expectations arose. Woman as nurturer, man as warrior. Woman as gatherer, man as hunter. Some of these also have some biological crossover.
Then we decided pink was for boys ,then for girls. Nice shoes; boys then girls. And so on. Foot binding, neck-stretching, tattoos and their placement, waxing, you name it we assign it. This GENDER stuff is assigned. And it hurts women (and men but I'm a feminist so I care if the patriarchy hurts women).
I am a woman, in all my bleeding, feeding gloriousness. I love myself and my sisters, I don't reject my womanhood. I embrace my SEX. But I reject GENDER in it's entirety. Not for me, but totally. Wear pink, drink pints, throw darts, wrestle a lion. You do you.
But if it's fundamentally about SEX you behave that way. And in the UK at least, rape is with a penis. It's is SEX based.
If there are groups that are based on GENDER (golf clubs, knitting circles) make them GENDER based if you want. But prison, sports, rape centres, DV shelters and the like, SEX based.
TL;DR sex is observed, gender is a cage.