Morning Scepticism: Conspiracy Theorists

Trying to fit patterns over evidence is what people do, but that can lead to putting a pattern over data that's not really there. A conspiracy theorist has set up a pattern so that they can never be shown to be wrong - that absence of evidence is proof of a cover-up. So if someone is at the point of taking contradicting evidence as evidence for their belief, how can they possibly be argued out of their position?