In WWII, the was no lessening of the "human element of War." That is exactly the reason we went to War with the Axis powers. You are perhaps too young, to fully comprehend this overwhelming fact of life. Regardless...I can say with full certainty- you will eventually understand what WWII was really all about.
I'm not debating why we went to war in WWII. I'm just stating we reenforce our training and use propoganda to lessen the "human" element of killing.
Read Dave Grossman, On Killing : The Psychological Cost of Learning to Kill in War and Society, it really goes into the subject.