Because there is one rule for trans people who are allowed to say whatever they want unfortunately, but another for women who may not even point out that women have vaginas any more without being deleted.
I was deleted and banned from Dismantle Misogyny on FB last week for saying the above. Comments calling me a disgusting TERF and others slagging of the personal appearance of another woman who who had commented were left to stand.
On Everyday Feminism last week someone posted that rape victims 'annoy her' as they use their victim status to further their TERF views and stop trans people entering their spaces because it supposedly 'triggers them'. Again, left to stand.
Another feminist on one of my online groups reported a comment to FB from a trans person about her 'white cis pussy getting raped and fucked' - she received a reply saying they would not delete the statement but suggesting that she hide the person instead if their views upset her.
I could go on. The upshot is if you are a man who says he is a woman or a feminist who supports transwomen you can be as rude as you like and make as many violent threats as you like and you'll get away with it. Dare to point out the basic facts of biology though, and you're a hateful bigot who will be deleted.
I don't know what we can do about it.