it's a matter of trust. let me demonstrate.

bush is in a hall speaking to a bunch of his sympathizers. he tells the crowd that the sky is yellow. they believe him, without going outside to look, even though he was told that's not true. he maintains that it is. then, everybody comes outside and sees that the sky is not yellow. but bush still maintains that he said what he said because of good intelligence. that he KNEW for sure, there was NO DOUBT that his information was correct. even when he was told he was wrong before the crowd went outside, he chose to believe what he wanted to believe and hence tried like hell to make us all believe it.

would the crowd trust this guy again? when is a lie a lie?