OK, let's go with him telling the truth now about his telling lies then. And that SH never had any, or was attempting to make any, WMDs. Nope, none, never happened, he was a great guy, generous to a fault, loving and understanding...we get that. The guy never did anything wrong.
Now, lets say that the guy who now says he was lieing then really had been telling the truth, and that no one believed him. And that SH was a murderous thug who had used WMDs on his own people, and was developing his NBC weapons, and actually used them to attack, oh, New York. The people who are outraged now because no one believed the guy who the assume is telling the truth now about telling lies back then would have been outraged then because nothing was done to prevent an attack that we had information about.
That is one of the problems with gathering information - you kind of have to assume a worst case, or almost worst case, scenario. Otherwise you are like Chamberlain, stepping off the plane and proclaiming "Peace for our time."