Some months ago, a poll showed that 50% of Americans believed that the majority of 9/11 terrorists were Iraqis; now a new poll shows that
1/3 of Americans believe that WMDs have been found in Iraq, and 22% believe that Saddam used them (presumably they mean in the recent conflict). This is put down to cognitive dissonance, and people's need to edit their perception to reconcile it with their beliefs; after all, it's easier to believe that you missed that one FOXNews program where the weapons were found (and which is consistent with everything you've heard before or since) than to believe that everything you've seen on TV and read in USA Today is a distortion. And then there is Cialdini's consistency principle; i.e., that if someone has made an investment in believing in a certain point of view, they will defend said belief, often to the point of absurdity, to avoid the shock of having their world-view dragged out from under them (extreme instances of this include religious cultists believing
whatever absurdity their gurus tell them and Creationists committing out-and-out fraud to "disprove" evolution).
Ah yes, cognitive dissonance; a fascinating phenomenon...