All Human Life Has Dignity
Just War Theory begins with an acknowledgement of the moral abhorrence of war. In the same way, any theory on torture must be rooted in the recognition of the moral abhorrence of torture. From a Christian perspective, all human life—even persons guilty of the worst crimes—has dignity. And the defense and promotion of our dignity has been entrusted to us by God. As Pope John Paul II wrote in his encyclical The Gospel of Life , “Man has been given a sublime dignity, based on the intimate bond which unites him to his Creator: in man there shines forth a reflection of God himself.” (EV 34).
One of the conditions of Just War Theory states that the use of force cannot produce evils graver than those to be eliminated. In the same way, in the use of force in dealing with prisoners, we must recognize the possibility that once we accept that torture is justified in one situation, avoiding its use in other situations may become more difficult. There should always be a moral presumption against torture in order to uphold human dignity.
The use of torture except in the most extreme circumstances (when the intention is to save innocent human lives) diminishes all those involved. It tells our enemy that in a sense he has already won because it signals that we are willing to descend to his level, instead of trying to compel him to rise to our level. As the most powerful economic, cultural and military power in the world, many other nations look to America for an example of what they can be, and of what democracy is.
The systematic use of torture would tell other countries that there really is little difference between us and the Islamists who take delight in torture and the killing of innocents for purposes of revenge, intimidation, humiliation or punishment. By applying the Just War Theory to torture, we can help create protocols that acknowledge the dignity of all human life and the abhorrence of torture while also creating a set of conditions that, if met, would justify the use of force to save innocent human lives.

It seems slightly ironic to say that the torturers are almost forced to sink down to the level of terrorists in order to keep the country safe and extract information. Perhaps there is no need to sink down a level because some people are already on that level. It is even more ironic to say that all human life has dignity but sometimes certain circumstances force others to take away that dignity in the most humiliating and painful ways. Christianity emphasizes treating other people well as the Golden Rule shows but torture can never be justified under these principles.
I would like to think that if we did go down to the level of using violence in order to interrogate prisoners we are:
A.) moving ourselves down to the level violence prone lunatics, of which using torture and and abnormal interrogation tactics are used.
B.) Setting an example to other countries in which if an American commits a crime against their home country the use of torture is justified as well.
C.) The fact that by causing someone pain we are effectively letting others suffer less? if anyone suffers at all shouldn't that be an issue as well?
Any intentional hurting of human life in the context of interrogation is torture, now the question is, would we be willing to do this to our own people?
Perhaps Catholics believe that all human life has dignity, but a Christian proof of this must be grounded in scripture (This, not to say that such is not the case, but simply that such has not been demostrated effectively in this argument).
On another note, the army that does not restrict its tactics in battle has an unlimited advantage.