I would argue that joining a PvP server is the same as agreeing to a boxing match. However, in said match you agree to not sucker punch someone in the nuts.
There's a certain aspect to their personality that can be derived from them being a boxer. It takes certain types of people to do that (as with almost all things in life). Same thing with people who get enjoyment from griefing (which has been defined already) others in a game. There has yet to be given a compelling argument against your actions in a game towards other people not being an indicator of some aspect of your personality.