"Actually it's quite fun to fight them, you know. It's a hell of a hoot," Mattis said, prompting laughter from some military members in the audience. "It's fun to shoot some people. I'll be right up there with you. I like brawling.
"You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil," Mattis said. "You know, guys like that ain't got no manhood left anyway. So it's a hell of a lot of fun to shoot them."
It's called Gallows Humor.
This guy didn't do anything wrong. We ask our military to kill people, and they have to be able to it. If they need to trivialize it just so that they can sleep at night, then I got no problem with it.
If a politician making decisions at arms lenght had said this, it would be a different story. That would be unacceptable, but soldiers are not polititions. They can say whatever they want.
There are a lot of 'crimes' that a soldier can commit during wartime, being a prick isn't one of them.