Those utterly unprovable "facts" that lead one down multiple rabbit holes. Real facts mean nothing. And won't put a dent in an adherent's viewpoint. Take chemtrails for example.

No amount of scientific explanation will shake these people out of their chemtrail stupor. They can actually see the contrails. So it MUST be chemtrails!

Of course, the more mysterious the issue, the more sinister the theory. And the more sinister the theory the more it MUST be the truth. This especially applies to politics.