While I may not have the tenure with KGB I do have the knowledge of the Warhammer lore to tell you most decidedly you are misinterpreting an awful lot if you feel destruction represents the side of evil. I would wager you have not truly dug deep into the lore or you have a very black and white sense of good and evil. The empire murders their own citizens routinely during this time in the lore, The high elves have turned their back on an alliance with the dwarfs to bolster the ranks of the empire as the people turn to the Chaos god of change due to the oppression of the emperor. The Dark Elves strike out against an enemy that attempted to commit genocide on their own race and split the Elven race in two. And the Green Skins believe in expansion through might of arms which the Dwarfs happen to be in the path of that expansion.

In the end motivations in this game are far from "their evil so they do x" and that is the benefit of the warhammer lore being as deep and rich as it is. Beyond that I have never once seen the least bit of RolePlay among KGB that is a big part of why I joined with them. Roleplay in a game designed for PvP always leads to poor conflict as you have to organize every raid prior to it's execution with the other side so that the battle has RolePlay significance. I have embraced KGB because it allows me to CRUSH my enemies on the battlefield, and no one seeks to be on the losing side of the fight.