One of my few shifts to the political right in recent years came from accepting retribution as an appropriate purpose for criminal punishment. I don't accept it as a way of achieving justice, but as a way of making the victims of crime feel better, whether the victims are specific individuals or society as a whole.
So the political valence of investigating Bush Administration members for crimes is interesting when it comes to retribution. Conservatives would normally think retribution is a fine reason to go after someone, while liberals might not. Now though, conservatives shrink at the idea that people would want revenge for the crimes committed in our name and with our tax dollars. They might want to think about how strongly retribution should influence punishment in all crimes then, not just for rich people drunk on political power. I suppose liberals might consider the same question for other crimes, too.
Finally, conservatives might argue that no retribution is needed, because the crimes weren't "wrong." That would be the most shameful reasoning, I think.
(A side note - if it's true that the Bushies ordered the forgery of evidence of WMDs and Al Qaeda in Iraq to keep the war going, we can likely add another war crime, a war of aggression, to Bush's list. Forging evidence seems to me to be a different category from simply withholding evidence that cuts against their argument for continuing the war.)