Sir, respectfully, this is far from correct. there are people who are just plain bad. relative to standards of the culture, "contract with society" and all that jazz even accounted for- there are people who just want to see and do bad things. i will strike a comment as such up as 'lack of exposure' as opposed to willingness of applying relativism of morals.
i had a long response posted that offered some of the things i've seen in my travels first hand, but they are personal and should stay that way. there is evil, and there is good i am certain. they may coexist (and do) in the same person (most people) with a ever fluctuating dynamic, but... there are some that are lost in whole and seemingly driven by the desire to be bad.
Drew, I know that given your own history as a soldier, you've seen a lot of things that whether you label it subjectively or objectively evil, are horrors that should never had occurred.
I think what AC might be saying is that a lot of those horrors were again a product of their environment. That some of the people you fought against, had they been born and raised in the USA, might have turned into model citizens and perhaps soldiers such as yourself. And that he's saying that some of your comrades in arms--guys you trusted with your life--had they been born into the environment in which you fought, would have become those evil people.
Essentially I think AC's point is that people are very much inherently malleable, and not inherently good or evil. It's a point with which I have qualified agreement; some people would turn out good in good situations, and evil in evil situations. They are absolutely a product of the environment.
I think your point is that some people are just bad. And it's a point with which I also have qualified agreement. There are people who are the product of loving households in affluent and tolerant communities, but something in them is so askew that they become sociopaths, or sadists, or elsewhere. Nothing in their external environment made them this way. Now, it might be their brain chemistry and not that they're just born immoral, but I can see your point in calling them inherently evil because it was their own internal problem.
So I think it's a mix of nature and nurture. Whether the "nature" is a chance mix of biochemistry or a inherent moral depravity doesn't matter for the purpose of how to deal with those people; they should be confined in such a way that their nature cannot cause the rest of us harm.