Lying to a jury is different from having muddled memories. Lying must include intent. If he was lying, he must be held accountable. There is no room for wiggle in the case of perjury regardless of whose ox gets gored politically.
Perjury is a vile act that undermines all justice.
Sure. If Libby is found guilty of having committed perjury, then he'll have to take his medicine. But I don't find his crime to be of greater interest than, say, stealing Top Secret documents out of the National Archives.