I'm a little bit sensitive about this issue, because I have a friend who just came back from Iraq, where he was an MP, and he's messed up. He's physically unharmed, but mentally/emotionally, he's just messed up, and (as much as he can or will articulate it) it's because of the things that he saw and the things that he had to do. And I don't mean that he did anything wrong or anything that he shouldn't have done - the things that were necessary to get the job done and to stay safe and to keep his men safe were also things that have been difficult for him to live with.
As a society, as a civilization, we have rules. You don't hurt people on purpose. You don't kill people. You don't take other people's things. We also have established exceptions to those rules; we've laid out circumstances in which it's okay to bypass those rules if it's absolutely necessary. If a guy's bearing down on you with an AK-47, you're allowed a waiver on the "don't kill people" rule. If a detainee has information that you need, information that could save lives, and he's not giving it up voluntarily, you get a waiver (to some extent) on the "don't hurt people on purpose" rule. But that doesn't mean that those rules don't go away, or that they aren't still important; it just means that, in some extreme circumstances, other rules are more important.
When we say things like, "We're turning into a nation of men raised by women," (and hello to the sexism, k thx, but we'll let that slide for now) or, "This civilization has been pussified," we're acting like it's a bad thing to recognize that yes, on the whole, you don't hurt people on purpose. That hurting people on purpose is the necessary exception, not the rule. Do we want to raise a generation of men who are so very, very manly that they don't recognize "don't hurt people on purpose" as a basic rule of society?
These guys are coming home and dealing with the conflict between what's necessary to complete the job there and what is societally acceptable here. That conflict is to be expected and shouldn't really surprise anyone. Instead of calling them pussies and telling them that they shouldn't feel bad for hurting/killing people, ("Hey, man, he was a terrorist! He hates your freedoms! What're you all broken up about, you pussy?") maybe we, who are sitting at home on our asses and not out there, could be a little more understanding.
I don't wish that kind of emotional turmoil on anyone, and we certainly don't benefit from interrogators who are so soft that they're not willing to invoke that "lives are at stake" exception and do what needs to be done. But nor do we benefit from someone who's willing to pretend that those basic rules don't exist at all and say, "Hey, he's not even human, so it really doesn't matter what I do." There is a middle ground, and these guys are the ones who have to walk on it.