So, this may seem stupid, but I think there needs to be some kind of punishment for psychotic behaviours on the server.
Yes, it's a PvP server and if you don't like the possibility of being PK'd you should not play here.
That being said, when certain players spend their entire day doing nothing but going back-and-forth through maps PK'ing everyone they see, then demanding payment for the psychotic behaviour to stop, I think that should warrant some kind of punishment.
*cough* ZooMweBG *cough*