Michael Ledeen, almost certainly losing his mind at the prospect of his pet war sailing out the window, had what amounts to a tantrum, complaining that there was no good reason for the Iranians to give up their nuclear weapons program. Yeah, ok, it would be a completely rational decision, but the Iranians are so kaaaaraaazy(!) that there's simply no way they'd ever do anything rational. So he assumes they didn't.
Personal experience, I suppose.
A more cogent complaint is "what's different now than in 2005, when we all thought they were ready to blow things up?" Well, lots of things are probably different. Sources and methods change and are improved, for one, but even better is the simple fact that the CIA et al probably aren't as worried about competing with stovepipes as they were, so they were able (and probably happy) to engage in "a 'very rigorous scrub' of 20 years of information, some of which informed the 2005 N.I.E."
See, unlike Ledeeen, the intelligence community appears to be trying to learn from its mistakes. Learn, and apply what it learned. And it would appear that in all that learning and application, it changed its position. I know the concepts I italicized are shocking and confusing to someone like Ledeen, who learned what his opinions were going to be when Scaife ponied up the dough, but the point of intelligence is speaking truth to power, instead of twisting everything to reconfirm your agenda.
He probably takes comfort in the knowledge that Israel is also disputing the report, but if the contradictions are as weak as this:
Mordechai Kedar, who served in Israel's military intelligence for 25 years and is a researcher at the Begin-Sadat Center for Strategic Studies in Tel Aviv, said Israel's intelligence community disagrees with the latest estimate.It's probably not much to put faith in. Aside from the fact that Kedar is pretty openly poisoning the well with that "only a blind man" stuff, the US and Israel do not necessarily share the same data: while the UK and the United States have (allegedly) a total information sharing deal, the United States and Israel do not.
"This is a matter of interpretation of data. I do believe that the U.S. and Israel share the same data, but the dispute is about interpreting the data. … Only a blind man cannot see their efforts to put a hand on a nuclear weapon. They are threatening the world."
Besides, the same problem exists as ever did for trying to dispute this sort of thing: were such a response really legitimate, Bush would have made it already.