Re: Good riddance!
Honestly, as described it seems SO did the right thing.
They do appear to have actively and vociferously announced that they utterly refuse to use preferred pronouns, after also repeatedly calling someone by a pronoun they really didn't like, despite being asked not to.
If someone says "please call me X", you damn well try to remember to call them X.
Using the wrong pronoun is no different to calling someone by the wrong name. You'll forget sometimes, but you should try to use the right one.
If someone decided they would never call you Zippy, instead insisting on calling you Bungle, even after you remind them that your name is Zippy, and they replied with "no, I'll never call anyone Zippy?"
That's not the act of a civilised person. That's the behaviour of a bully.