Obama is handling this very astutely.
Rather than push for prosecutions or investigations, which would make supporters and apologists of the Bush atrocities band together and initiate a propaganda offensive to combat it, he is avoiding direct conflict and letting facts leak out and accumulate in the press and in the reservoir of common knowledge.
Today, even conservatives grudgingly acknowledge Joe McCarthy and Richard Nixon were paranoid SOBs, but if either had gone to prison for their crimes, they would still have defenders out there trying to rehabilitate them and rewrite history.