How does that make it a bad comparison?
That is why in MMORPGs fights to the death are the way to go. If you suffered full XP loss (the normal death penalty in MMOs) when you died, then I can gurantee you that killing your opponent in a duel (say in EQ2) would have a stigma attached to it. Thus, you would have more fights to half life or some other non-lethal combat.
Like PvP in D&D should be.
EDIT: Here's the point:
PvP is combat that is fun for both parties.
PKing is killng the other person when they don't want it.
That is the distinction I was trying to draw. There's a difference between PK and PvP. PvP isn't, in my mind, defined as antagonistic behavior that is only done to rile up others or make youself feel bigger. PKing generally is.