"Belief in belief" exists as a phenomenon but is neither necessary nor sufficient to explain the claims of the Dragonist (if I may name his espoused metaphysics thus) in Sagan's parable.
My most recent encounter with someone who believed in belief was someone who did not in addition believe. He had believed once, but he lost his faith (in this case, in God, not dragons) and he wished he could have it back. He believed in belief--that it was a good thing--but alas, he did not believe.
In the above article, Eliezer (if I may so call him) was invoki...
It would be difficult to say what this evidence would be. As one who has spent some time with people who would generally be called deluded, I can assure you that finding an understandable explanation for their delusions is non-trivial.