One of the things that I almost always say to people who don't have an issue with torture is, if our troops are captured by the enemy, is it OK for them to be tortured? They almost always laugh at me and say that's ridiculous. But it really comes down to the golden rule. Do unto others as you'd have them do unto you.
That may seem silly to say in a war, since you're killing people, but if you are trying to fight a "moral" war then I say it again, you need to be above reproach.