Inside the beltway prosecuting Bush and Cheney is inconceivable. The universal belief that it can't/won't/shouldn't happen is a conclusion in search of a rationale. All the false memes, lame excuses, immoral excuses, and irrational blather serve to defend their 'reality.'
"Looking forward, not back" and its cousin "making sure it doesn't happen again" (instead of punishing those who did "it") are among the the most insidious of the false memes. Another is the bipartisanship doctrine -- the notion that the public wants Dems to "work with' the torturers. Out of the bipartisanship doctrine comes their fear of 'backlash' -- the absurd notion that "the public" would "rise up" against them if they labeled corrupt people and accused them of their crimes. (The dreaded "politics of personal destruction.") They are so far gone they believe that simply failing to show 'respect" to the wrong-doers in their midst would upset us.
These assumptions are, of course, the opposite of reality. People love to see champions go after villains. Our government isn't corrupted by some abstract 'process' or force that needs 'fixing" so it "won't happen again." It is corrupted by people who abuse power to advance their own agenda -- people who must be punished for their acts. Stories of heroes who get the bad guys are the meat and potatoes of engaging entertainment for a reason -- they reflect our need to protect ourselves by going after the bad guys in real life.
The damage done by the bizarre beliefs is exacerbated by the beltway brand of "risk-benefit" analysis that focuses solely on the "risks" (which are, more often than not, irrational fears). When standing up for principle would require condemnation of the opposition, or would otherwise challenge 'business as usual' status quo, they are driven to "stand down" by their fears of some "bad thing" that will happen. Any benefits of fighting on principle, or negative consequences of failing to, have no place in their "thinking" (i.e.,
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=389&topic_id=5447507&mesg_id=5448828">the non-thought of group think). Their fear of arousing the mythical backlash beast and aversion to 'personal attack' (which might earn them dirty looks at cocktail parties) trumps all.