We have solid evidence
Bush claimed there was substantial credible intelligence of WMD sufficient to pose a real threat to the US.
How credible is intelligence with no hint of location? Granted, a piece or two of credible intelligence may appear that lacks geographic references, but for the most part, credible intelligence is credible because it identifies places, names, objects, that can be verified either physicaly or by cross-checking with other intelligence. You would have to be a 21'st century "journalist" to bet on a source that can't be checked up on. You don't bet billions of dollars worth of equipment and the lives of US military people on unsubstantiated rumors. And in order to substantiate, you need places, names, and objects.
You don't honestly do that on the basis of not having records that don't balance regarding weapons that, if unmaintained, are unusable. I've worked for far less unreasonable bosses than Saddam, and the fact that he ordered the weapons destroyed would not have protected those who destroyed them from his wrath. It is quite possible that the weapons were destroyed and those responsible simply didn't want to expose themselves by reporting it. Or the records could be off due to errors.
Once you have that intelligence, and free run of the country, and no need to continue to protect sources now that the threat is neutralized, you go in and you find it (well, no, "find" is the wrong word - you know where it is, maybe "get" is the word) and take care of it.
We are talking about substantial weapons programs - chemicals, biological agents is quantity. Not the One Ring or something else tiny. Big, nasty stuff that is real hard to clean up. Not as big as a similar conventional weapons program, but much harder to clean up. And if we have reliable, credible intelligence, we know where at least some of it was at some point, because otherwise we don't have any way of either cross-checking the stories or getting some physical observations from sattelite or arial surveilance. If it was all mobile, reliable, credible intelligence would have warned us of that fact. Without cross-checking or physical observation, all you have is rumors.
There was a lie. Was it that the intelligence existed? Was it that it was credible? Was the intelligence an elaborate web of cross-checked lies that fooled the Bush team?
The absense of evidence is not evidence of absence - there may be a substantial WMD program. But I'm not saying there wasn't - I'm saying that Bush lied about having reliable, credible intelligence about one.
The evidence of a campaign of lies is far more solid than the evidence of a substantial WMD program.
As the Bush campaign was fond of pointing out, lies are a bad thing.
