In all honesty and despite I am NOT a personal fan of it. As PvP/Friendly fire is already built into the game why not have an option on the server to enable it? As long as pre log on an alert came up so there could be NO CHANCE folks would join unaware of this have it it. Whatever floats your boat.
It seems daft that such a minor tweak isnt in the game to expand its appeal to those that like such things