...it is the nature of a conspiracy theory that all information must pass through a very discerning, yet simple, filter. Information that is confirmational is accepted; that which is contradictory is rejected.
Conspiracy theories have the self-sustaining gift of ramification: They sprout new tendrils, like a mad vine that has invaded from another continent. For the committed conspiracy theorist, there is always another angle to explore, another anomaly to scrutinize.
[emphasis mine] And:
These theories do not always find a purchase on one distinct portion of the ideological spectrum. What they have in common is the emotional investment of the believers: The theory becomes not merely a hunch or a notion, but rather a core belief that is part of the believer’s identity. The person isn’t going to abandon the faith simply because a piece of paper surfaces that would seem — to others who are not so invested in the theory — to refute the central notion.
“It’s easier psychologically to come up with a rationalization than it is to admit that you were wrong,” said Ronald Lindsay, president of the Committee for Skeptical Inquiry, in Amherst, N.Y., publisher of the myth-debunking magazine The Skeptical Inquirer.
“If you have a pre-commitment to a certain point of view, and that point of view is important for your identity — if you are emotionally attached to it — your emotion is going to shape your reasoning process. You’ll be presented with facts, but you’ll find some way to minimize the significance of those fact,” Lindsay said.