@BeckyAMumsnet, I have another question about the threads which @PandoraSocks linked to in her OP.
Your moderators are clearly aware of the threads in question as they have zapped some of the posts. Do they not look at the wider content of those threads and think "this is not in the spirit of the site, we need to take the whole thread down"?
I honestly don't understand it. You say that racism is unacceptable, and I do believe that you genuinely think that, and yet some threads with post after post of racist bile are left to stand, perhaps with the odd post being deleted here and there to suggest a token effort. Why can't you just take them down when the whole thread descends into hate speech?