Yes, CarolC, the logical fallacy there is this:

Using UN resolutions being violated as a reason for attack presupposes that the UN's wishes are to be respected.

BUT the UN decided NOT to attack Iraq. Why not respect THAT wish too? Or else respect neither wish, and then give up the resolution as a pretext for invasion?

Anyone using UN violations as a reason to attack is having his cake and eating it, saying that we should listen to the UN only when they say what we want to hear, and otherwise ignore them. Thus, what the UN said becomes a red herring.

Same with the weapons inspectors. People use the content of their reports as a reason to ignore their recommendations. But if their recommendations are wrong, why assume the other parts of the reports are right?

In both cases, the administration took the outcome they wanted (which we know the neocons had wanted for a long time), looked for any statement made by anyone that could support their position, and ignored any statement made by anyone that did NOT support their position; often, this entailed accepting the validity of a person's opinion about one thing, and rejecting the validity of the same person's opinion about something else, with no justification beyond "it gives us the result we want."

You would never get away with this kind of reasoning in science, but in the "art of war" it appears that no-one looks too closely.