You don't really get it....
It's not that PvP players break rules more or PvE players break rules less, it's that PvP players have MORE rules that breaking would directly affect another player. It's hard for a player to get the motivation to report somebody for breaking SoD rules w/ proof let alone even know rules are being broken. In PvP there would always be some victim, legitimate or not, that demanded retribution to whatever griefer slapped them in the face.
And really, PvP zone mobs...

syduck:
If pvp were ever to go large scale it would be in the form of MQ faction pvp with incentives for those who were pvp flagged. This is after the whole class-balance elephant in the room is taken care of.