Jonathan Chait spells something out that ought to be obvious, yet somehow seems to have escaped many apparently intelligent people:
The right's newfound outrage [over the idea of prosecuting the people responsible for torture] is a more hysterical manifestation of the mainstream sentiment that it would be an unseemly form of vengeance or "looking backward" to hold the previous administration legally accountable for torture. It's a bizarre sentiment. The prosecution of any crime is inherently backward-looking. We prosecute law-breakers to keep them or others from breaking the law.
He adds another ought-to-be-obvious observation:
The most common defense of waterboarding is that we subjected our own soldiers to it. That's true–as a way of training them to withstand enemy torture. When you reverse engineer a torture-resistance program, you're almost by definition engaging in torture.
Actually, the whole column is worth reading.