Werewolf:
Not so. Understanding changes things. For instance, and as a hypothetical example: Whaling can be justified on the basis that whales are animals, with animal intelligence and no self-awareness. But suppose at some time in the future, a method of communicating with whales is discovered, and it becomes clear that they are as intelligent as humans, and are fully self-aware. At that point, whaling becomes much more difficult to justify, since it is now known to be the killing of individual, self-aware, intelligent creatures.
Does that make earlier cultures that killed whales for food suddenly more evil? No, it makes them ignorant of this hypothetical future knowledge. Judged in the light of what was known at the time, they were doing nothing intrinsically wrong. Judged in the light of this hypothetical hindsight, they were committing murder.
As understanding changes, so must morality.
Would you punish a small child who killed a man, in the same way that you would punish an adult who did the same thing? No, you would not, because the child's understanding and, as a result, his moral framework, did not give him the capacity to understand what he was doing at the same level that the adult could.
Just as children grow and develop deeper understanding of their world, and in so doing acquire a moral code (whether or not it is one you agree with), likewise cultures and societies do the same thing.
A society (or a person) cannot be judged to be evil for doing something that it did not realize was wrong. Ignorant, yes. Evil, no.
-BP