I know you didn't say they should be able to do whatever they want, but its what implied. What prevents them from doing whatever they want if they don't have to tell anyone? The simple answer is nothing.

They must tell the people everything, or else we have no way of knowing what they are doing is right or not. If something is highly classfied then of course they don't have to go on TV and tell everyone, though they still have to tell congress. And how they treat prisoners is not top secret information. Who they are are, what they do with them, and the reason they are there, should all be public information. Where they are being held, and details of their actions may be secret if its important to our security.

In this case, torture is something that should never be hidden. Yes people will complain and cry about it, but that is because its wrong and shouldn't be done. They know the country doesn't want anything to do with, which is why they are hiding it, and thats just as wrong.