My main objection to torture is moral. I ascribe to the normative proposition that torture is evil. There is, however, no way to argue this position rationally. Someone else might very well reckon that torture is not evil or that torture is evil but excusable under certain circumstances. And there we'd be at an impasse in ten seconds flat. It's evil. No, it isn't.
I have other more rational objections that are subject to discussion up to a point. One is an ethical consideration. We ought not to torture because to do so subjects us or our compatriots to torture and it makes us appear barbaric. These have serious consequences for the success of our government in its pursuit of foreign policy and national security objectives.
The question then turns to whether these consequences are outweighed by the benefits to be gained from torture. I rather think not. It is my understanding that statements elicited by coercion are unreliable and that the best that we can hope for with torture are false confessions for propaganda purposes. A little questionable propaganda is hardly worth taking the low road.
Of course, one may dispute the factual bases for my opinions, but I have yet to have the pleasure of discussing the issue with anyone who knows anything about the supposed benefits of coerced statements.
Finally, torture is unlawful. If the adminsitration wanted to torture lawfully, it could have gone to Congress and asked for legislation that made torture lawful. It did not do so even in a political atmosphere where the Congress probably would have gone along with it. To allow the administration to evade the law with impunity sets a dangerous precedent and erodes the balance of powers.
Finally, torture is evil.