Richard Armitage is the one who outed Valerie Plame.
What, exactly, is it that you think Libby did wrong, other than cooperate with the prosecutor?
All he would have had to do is use the standard Hillary Clinton response, "I don't recall," and that would have been the end of that.
What exactly was it that Scooter was allegedly guilty of? Do you remember?
It was "perjury" -- lying to a grand jury. But what did the perjury concern?
Specifically, Libby testified that Tim Russert had told him that Valerie Plame was Joe Wilson's wife and was a CIA agent. Russert remembered the conversation otherwise.
He said/he said. That's the whole case, in a nutshell.
And a DC jury, fervently wishing it was Dick Cheney who had been charged, was only too happy to find Scooter Libby guilty of...well, something.
Contrary to your assertion, there is no real evidence that Scooter Libby was guilty of anything.