If the administration came out and said there was a connection to specific terrorist attacks on the US by Iraq such as 9/11 or OkCity the world would not have baulked at us taking action against them so I wonder why they did not do so int he first place. After the fact at a time like this makes it look as if they are searching for a justification since the WMD claims are not around as we claimed them to be.
Even though I do not support the US roll of global policeman and our interventionist policies I would have supported a strike on Iraq if they took out our embassies or the trade center, etc. Personnally I do not think we had to be at odds with Iraq all these years or back in 1990 either but even so a country can not allow a strike like we took without taking substantial counter action (not Clintonian tokanism). I supported our action against Afghanistan but not Iraq because as you said the justification given were "irrelevant" for the latter but substantial for the former.