They may not be against the rules (as of now), but let's be real... there's no need for it. I mean if it wasn't for TOS, we'd still probably see swastikas everywhere and people would try and justify it some way or another, and like some other people have said- this is gmod. It's meant to be a dumb, goofy, brain rotting but fun and enjoyable experience.
It's not fun when people start making comments about real life crap that most of us are trying to escape from for a bit. Don't know about you or anyone else, but it's exhausting seeing people talk about and even joke about this kind of stuff in chat when most of is just wanna do battlepasses, quests, hang with friends or do whatever.