I mean... if you're raised as a decent human being, killing somebody is against every moral thing you've ever been taught. And so, generally, in combat it's 'krauts,' the 'gooks,' the 'yanks' - whatever you want to do to try and make it so that it's not a human being.
I mean, if you're proud of what you've done when you've served in the military, well then we call that bragging. And if you are unhappy about what happened, we call that complaining. And so what are you going to do?