At what age were they made Nazis? Those who killed were adults, and adults don't transform. Adults who become killers do so simply because they are evil, simply because they are killers; there is simply no kind of transformation in adults, only in children. Even if I keep telling you all my life that the Nazis were killers, you would deny it because you are an adult. 

 That logic and reasoning is false.

So everyone in the US Military is a killer because they served their country? 

 yes, but they are not called killers but heroes. A king can order you to do this or that, but you can't give this excuse to your conscience.