Good post. Cognitive bias is something all people should study and look out for, as well as other mental phenomenon like false memories. For the former, I liked the treatment given in the book Nudge.
That said, while some are too far on the conspiracy side, some are not nearly far enough. We know that the desire for something to be true can cause someone to disregard negative information. Many people desire for conspiracies to be impossible, and so will always write them off. Bring them verified proof of past conspiracies, and they may accept it, but will not change their assumptions regarding any unconfessed conspiracies.