You certainly have the right to ask and it has been my experience that, if you ask politely, you will be left alone after the first kill. But they also have the right to play the game as it is designed and in a PvP zone, everyone is fair game, whether they asked to be left alone politely or not. Being killed in a PvP zone should never be the reason a GM disciplines a player. And no, we don't need open zone PvP.