This post is not about the morality of the use of torture. If a person thinks that torture is acceptable under certain contingencies, there is very little I can do or say that would convince them otherwise. Never mind whether or not it's right or wrong for now, would torture make us safer?
The US already has a reputation for inhumane treatment of "detainees". This is hurting our efforts in the war on terror for two reasons.
1.An enemy is that much less likely to surrender if he thinks he's going to be badly treated. Normally, when a combatant is surrounded and there is no hope for victory or escape, then it is considered advisable and acceptable to surrender. But if he thinks he is going to die anyway, or suffer a fate worse than death, then he will likely decide to take down as many of his opponents with him rather than surrender. Remember that the closing days of WWII, the Germans stood and fought against the Soviets but surrendered to the Americans and the British. Having a reputation for savagery might deter people from going to war against you in the first place, but once the war has already started they will that much more resolved to defeat you. All wars end when one side or the other (sometimes both sides), loses their resolve. Our goal should be to weaken enemy resolve and not strengthen it.
2. It's bad PR. How our allies view us matters. How potential allies view us matters. But how our potential enemies view us matters most of all, because we want them to remain just potential enemies and not actual enemies.
Proponents of torture point out that Allied operatives during WWII carried poison capsules in case they were captured, so that they would avoid being tortured. They argue that the Nazis used torture during interrogations because it worked. But intelligence gained during torture sessions has been established to be faulty. The Nazis used torture because they were sadists. Are we sadists too?