People turn warmode on either to pvp, or for bonuses. You turn warmode on to waste people's time, because you have no life of your own, and your only source of entertainment is making others angry. Also, you know you suck at pvp and can't kill people your own level, so you gank lowbies. They know you suck at pvp, and they know they would murder you if things were equal, so they get mad they're getting killed by scrub like you.
Also...did that really deserve it's own thread? Even 8 years old could answer your question.