You would need an "universal code of ethics" to state that.
Sure. Anyone at the receiving end of an ork waaagh would deem them evil (except maybe other Orcs, Drak Eldar and Tyranids). As anyone else would who was on the receiving end of a war. Hunns? Evil. Persia? Evil.
Actually lore implies that orcs are some kind of biological weapon unleashed by the old ones in the last desperate stages of war. They are the same kind of "evil" as a bomb or an alligator attacking a human. they do what they where created to do.