Tolkien and the Monsters

[Firefoot]

So why label creatures as evil if they are only defending themselves from unknown creatures, or ones known to be their enemies in the past?

I think the problem I have with that statement is the word "defend". In cases such as Moria, Parth Galen, etc, and in events including most of the examples of evil, they are not merely defending themselves. They are launching an out-and-out attack on the unknown creatures/ known enemies. In Rohan, the Orcs were killed because they had made battles with the Rohirrim in several occaisions, and recently, and lauched raids on their farms etc.