Well, I think that he just some crazy lunatic who thinks he can get away with it, or just some stupid guy who thinks it is funny. If he is being serious, then that falls under harrassment.
I don't think calling them "child abusers" is accurate... I've seen people like this plenty of times, simply contact a Moderator or SHOPS, and delete and ignore the harassers. I didn't see the comments, but this works for a variety of problems with certain members.