Though I can't speak for Admin, I am pretty certain that he will simply tell you that that is why the "blacklist" option exists, bella.
In the 300 years I've been a member here, I have seen dozens of malicious and spiteful members come and go. Some of them even gleefully and openly admit that they get their jollies by being nasty. It's sad, but there isn't much you can do except to STOP FEEDING THEM.
They thrive on nastiness and conflict. If you blacklist them, they not only "starve", but other people see how crazy they are when they keep screaming for negative attention.