If you must prune nasty messages, how about replacing them with an emotionally neutral paraphrasal? You know, like "User 4360 invited user 7290 to go forth and multiply." Or "User 3265 speculated that user 12365's mother wears footgear normally reserved for persons in military service."
It spares me wondering what the heck could have been so horrible that it got pulled in a thread as rough as this one.