The Libby case is different because what Bush did was commute the sentence for someone who was committing a bad act on behalf of Bush (and Cheney).
It isn't that the President exercised his constitutional powers, it is that he is furthering a cover-up. That is the sand in the eyes of Fitz's umpire.
The outrage is over Bush's continuation of the cover-up. Had he not commuted Libby's sentence, then the DOJ may have been able to extract information from Libby as to why he lied in exchange for a lighter prison term.
So, in spite of all of his protestations over the years that he wouldn't comment on the Libby case because it was in the justice system, Bush's action just pulled the rug out from under the Justice System.
What if Nixon Had Pardoned the Watergate Burglars
Rather than compare Bush's act to any of Clinton's pardons, Bush's action should be compared to whether it would have been appropriate for Nixon to pardon the Watergate Burglars.
Can you imagine the outrage if Nixon would have pardoned the Watergate burglars. He must have considered pardoning them to keep them all quiet.
The Watergate burglars were committing crimes in furtherance of the President's agenda.
Libby committed felonies in furtherance of Bush's agenda.
Clinton's Pardons Are Irrelevant to Bush Commuting Libby's Sentence
I'm so tired of hearing the talking heads on the cable news shows argue that Bush was right to commute Libby's sentence because Clinton pardoned Marc Rich or Roger Clinton (or any other pardon they raise).
Clinton wasn't pardoning anyone in furtherance of a coverup.
Also, it is simply childish to even raise Clinton's actions. That is something a kid says to his mother to explain why he crossed the street without permission -- because Johnny down the street did it. It didn't work when you were a kid and it doesn't work now.
Any bad act by Bill Clinton is not relevant to a bad act by George Bush. Even if Clinton did something wrong, his actions do not make Bush's action right.
Why don't any of the Democratic talking heads even say that?!?
What Was Libby Hiding
I think we should be asking the American public to think about what Libby was trying to hide. Libby was a high ranking government official and an attorney. He knew what it meant to lie to investigators and a Grand Jury. He was convicted of lying -- he was not convicted of having a faulty memory.
Libby was covering something up, and Bush is just continuing the coverup.
That is the outrage.