online interactions are not rated by the ESRB
the rating you see is for what content is in the game by the developers, but they cannot help what other people say and do
it's the nature of the game being an MMO

I don't think you'd have a lot to stand on with reporting them either
in fact, if you whip up a frenzy and get a bunch of people specifically to report these places then it could be seen as harassment, depending on how far it goes