The permanent danger of torture through human history is that it can be used by the torturers to manufacture or "create" evidence through confession. In fact, this has always been the prime function of torture: not to discover something that the torturers did not know beforehand, but to force a victim to tell the torturers what they were already convinced was true. If there is no evidence of a crime, or if the evidence is flawed or tainted, one sure way to convict someone is getting the suspect to confess. This is how an honorable man like John McCain came to sit in front of a camera and say things that were untrue and that incriminated him and his country. The confession then retroactively justifies the torture. See: he admitted it! He was a spy/traitor/heretic/terrorist/conspirator! Just watch the tape.
When neoconservatives, at the peak of their hubris, bragged that they could create reality, they weren't kidding. Torture is the most effective means of creating reality because of this dynamic. What better evidence is there that someone was an al Qaeda member than that he confessed to it? And torture can get victims to confess to anything if they are tormented enough.
And so when Rumsfeld and Cheney And Bush repeated that all the inmates at Guantanamo Bay were "the worst of the worst", they were merely telling us what they were intent on proving. There was no way independently to confirm this lie - because no one else could see inside their circle of torture and abuse. No one else could subject their claims to independent scrutiny at the time. And if it were not for the Supreme Court, we might never have been able to do anything but take Bush's word for it.
I voiced this fear a while back, in a post called "Imaginationland." This was my fear:
It is perfectly conceivable that the torture regime - combined with panic and paranoia - created an imaginationland of untruth and half-truth that has guided US policy for this entire war. It may well have led to the president being informed of any number of plots that never existed, and any number of threats that are pure imagination. And once torture has entered the system, you can never find out the real truth. You are lost in a vortex of lies and fears. In this vortex, the actual threats that we face may well be overlooked or ignored, as we chase false leads and pursue non-existent WMDs.
This is how totalitarian regimes justify themselves: by inventing enemies and proving their guilt through torture. The parallel dynamic in such regimes is that torture itself needs to be concealed, and errors of judgment, which could discredit the regime, need to be covered up. The techniques used by Cheney were, after all, once used by the Gestapo precisely to avoid the public embarrassment of clearly physically destroyed human beings, to present the appearance of normality, while behind that screen the psychological warfare of torture could proceed unimpeded. And if an error were made, if someone totally innocent were captured or tortured, the regime could then torture the victim to say he was guilty after all. In this closed loop, there are no loose ends. The executive is always right and its victims are always wrong - and torture provides all the evidence you need to prove it.