So why is this guy any more credible on Iraq's nuclear program than other defectors and ex-scientists who have given us different accounts?

Imad Khadduri has been the single, primary source for almost every article debunking the idea that Saddam was trying to build nuclear weapons. His writing can be found in great abundance on almost every leftist anti-war webpage. Why is it automatically assumed he is not the liar, instead of other defectors and former scientists?

A frequent pattern in the anti-war movement: defectors that agree with us are telling the truth. Defectors that don't are lying.

It should be noted that the story that the Iraq nuclear program was not going well is irrelevant, compared to the fact that the program existed in the first place, and demonstrated Saddam's ambition for such weapons. It should also be noted that the pre-Gulf War nuclear program was rebuilt in a stealth fashion after the Israelis wrecked the first one, indicating that the ambition was a strong one. A pattern of behavior means something.

And if one assumes the Iraqi scientists were generating information designed to make Saddam think they were building bombs, in what way can Western intelligence forces be blamed for coming to a similar conclusion?