@Scottydamion,
Sometimes I think that evil doesn't actually think or reason out it's actions and that is why it does evil things. I like to use the knight and the dragon as examples since people can easily comprehend what I mean.
There is a knight and there is a dragon, from which perspective is the evil? If the dragon has never done anything evil is it still evil? The knight might just label the dragon evil because it is not a knight, even if the dragon has never done anything evil. The knight might even justify slaying the dragon even if it has done nothing evil simply because it perceives the dragon to be evil. So now who is the evil one? When the knight shows up at the dragon's lair to slay it, isn't the knight the evil one from the dragons perspective?
This simple little story based reasoning, I can conclude that evil often times neglects to rationalize it's own position and just acts without consideration. This is why I say, "A good person can become evil if it tries to destroy evil."
Christians tend not to like my reasoning here since they are certain that evil should always be destroyed. With that line of reasoning, I point out to them that they will become evil if they attempt to destroy it.
A truly good person can not destroy anything because they must allow the evil to exist because those are the rules a good person lives by. You often see this in movies when the good person pardons the evil villian during the final scene. But then the evil villain always forces the good person into killing them anyways which actually goes against the whole premise of the good position.
Nazis killing jews happened because they either rationalized themselves as being superior to jews or they neglected to rationalize their motivation to begin with. If they saw the jews as being the evil in their life, they will conclude that they should be destroyed. This is what people jump to, even though I have proven that it makes them evil to do that. Thus this is why we can now reflect back and label nazis evil. If you want to destroy them you will have to become evil in the process. That is exactly what happened too.