The people who are anti sexism (or 'sexism' as it should be written) are the people who have been driving the most recent moral panics about games and who have been acting unethically in the games media. So when they have come under criticism for this, they have screamed sexism (and racism and everything else) and played victim, despite being at fault.
And people have uncritically believed them.
So there's two intermingled battles going on. It's the 'SJWs' who are the biggest source of censorship, moral panic and ethical breaches in the gaming hobby at the moment and so attacking them is seen - by the naive - as an attack on 'diversity', when it really isn't.