More like "kill orcs because they are monsters that run around and kill things for fun"
Garrosh is the ideal orc, by the way. Thrall is more like a human.
all in my GW opinion, of course 
Actually, the Horde is probably less destructive than the Alliance are.
Although, the "nicest" race of all is probably the dwarves, while the "meanest" is the undead.
But really, the humans have a really corrupt government.