Unfortunately in the real world bullies exist. In-game bullying is difficult to spot as persistent killing of a player could be bullying or could be the result of the player continually moving into an area to be killed. My comments here don't include cases where there is a war between two alliances but are about one on one bullying.
Wars between alliances make bullying an even more difficult thing to spot or deal with when it can be a big alliance 'controlling the centre' or targeting of an individual (or small group) by an alliance.