I run a 100 member group for a game of mine that I play, and have for 5 years. Completely anonymous so this stuff hasn't caused any issues. Plus it helps too that I have full control over the accounts in it (can delete messages and ban people for any reason) but thankfully do to the anonymous nature nothing crazy has really happened. Although I'm sure if there was voice chat I'd have to be a lot more vigilant to prevent this stuff.