I've got a novel that I've been shopping around, a bit of "space noir" about a protagonist with a Dark Past. You surmise fairly early on that, at some point and among other things, he tortured people. (Let me note that I wrote the story before the Abu Ghraib stuff happened, so I wasn't being topical or anything).
For that matter, what I'm going to say here isn't really topical; it's just some background rumination.
People who have looked at the problem carefully know that torture is not a very good way to obtain information, because basically someone who is being tortured is trying to get the torture to stop, period, so they'll say what they think you want to hear. Moreover, (again, according to people who are expert in interrogation) there are better ways of getting information from those who might have it and might be disposed to tell it, under the right circumstances.
Nevertheless, torture does "work," given the right notion of what "work" means. It will obtain confessions -- if you don't care whether the confession is true or not. It will deter. It was noted that during Desert Storm, Iraqi soldiers preferred to surrender to U.S. troops than to other members of the coalition; I doubt that this is true anymore (even if there were still a coalition), so that's one aspect of "deterrent." Torture does punish; it just happens to be part of that "cruel and unusual" thing that we sometimes hear about.
But, as we are reminded fairly often, a good many of the people who have come to be "subjected to unusual methods of interrogation" by agents of the U. S. have not been convicted of any crime, and there is reason to believe that many of them were simply in the wrong place at the wrong time, rather than being part of some nefarious scheme to produce 9/11, the Sequel.
Some have suggested that this is the result of racism or something like it, that simply because the prisoners are Arabs (though many of them are actually non-Arab Muslims), they are being scapegoated. Or that it's actually religious bigotry against Muslims. That's consistent with the facts on the ground, anyway, and I'll stipulate that this is probably among the reasons why some people support the practice.
But let me suggest another possibility here. Torture isn't just about punishing those who are being tortured. It isn't even about punishing Muslims generally.
In my view, Guantanimo and Abu Ghraib are part of the ongoing culture war in the U.S. Partly it is about the culture of toughness, one group of people showing how much they are not "bleeding heart liberals." Partly, it's to intimidate enemies. But that doesn't go far enough either. The mere fact that the U.S. sponsors torture causes pain to one side of the culture war (you know who you are). And The Other Side likes that it causes you pain. It's meant to hurt you, plain and simple. They hate you that much.