You might be right about some PvPers but that shouldn't cast a cloud over the fact that it is now a PvM concern (at least it is to me). I don't wish for my concern to be dismissed simply because it happens to be a shared concern of people that aren't 100% legit players.
If a bank is robbed and half of its customers are criminals you can't just say "Hey, you guys are criminals and therefore have no right to ask for justice!" You might be right in feeling that it is somehow karma unfolding for those criminals but you can't ignore that the other 50% of the bank's customers were law abiding citizens with a legitimate right to express outrage and demand the robber be caught and justice served.
In a game where most damage wins, this multiboxing in PvM activities really needs to be addressed.