War is hell

Paul Helm raise this potential objection to "torture":

But we might wonder even more at an army who will train some of its soldiers in the slow and intentional infliction of frightening pain on the enemy, to wrest information from them. What psychological scars will using this procedure as a routine leave on them, as well as on their victims? 

Fisher emphasises the morally corrosive consequences of training people to be effective torturers:

Torture adversely affects the character of those involved in the process; both the torturers and the tortured. We are, therefore, rightly concerned over the sort of people that the public officials, whom we appoint to conduct special interrogations on our behalf, may become through their practice of torture. Virtues are crucial to our moral lives. We want our public servants to be men and women of virtue. Yet we need our special interrogators to be – professionally – men or women of vice. If they are to excel in their profession, they will need to learn to become in the exercise of their official duties, at best, indifferent to the pain of those whom they are interrogating and, at worst, adept in the vice of cruelty.[22] 

http://www.affinity.org.uk/foundations-issues/issue-66-article-4---war-and-new-testament-ethics

Several issues:

i) If we're dealing with a terrorist, then I really don't care about the psychological scars he will suffer.

ii) This also depends on the definition of "torture." What about painless techniques like sleep deprivation, sensory deprivation, or exploiting phobias?

iii) Finally, this argument proves too much. Suppose coercive interrogation has a hardening effect on the interrogator. Suppose that makes him morally or emotionally callous to some degree. No doubt that's bad for the interrogator.

But unless you're a pacifist, that's equally true for soldiers in combat. Take the infantry. Take soldiers who shoot people, toss grenades, then see the mangled bodies. After a while, they become desensitized. 

Same thing with field medics. Patching up maimed soldiers week after week and month after month has a numbing effect. 

Warfare can be psychologically damaging to soldiers. But if you believe in the right of self-defense, then that's a necessary evil. Likewise, law enforcement can make policemen very cynical. Does that mean we should disband the police?