As the countless hordes of demon armies walked by, the earth would become scorched plains, and the air would be filled with the scent of sulfur. Rubble and dead bodies would become the mainstay of the world.
If there was one racial prejudice throughout all the lands that could be viewed as natural and correct, perhaps the only one that could fit the bill would be the prejudice against demons.
As the representatives of Chaos, they indeed never did anything good. They would receive joy from killing other lives, with death and pitiful screams being the marching music for their armies. Souls were their food and replenishment, and even the existence of the undead, which brought death everywhere, was the creation of an ancient demon.
Add on the fact that they always played the bad guy in every Holy War, and even if it was a bit overboard to call them the root of all evil, it wouldn't seem strange to consider the demons as the final antagonists.