What often distinguishes the crackpot from the visionary is whether they are eventually vindicated. The latter usually begins their career being perceived as the former.
This is a tautology. Of course visionaries are the ones who were vindicated.
That doesn't mean that being perceived as a crackpot is a reliable indicator of being a visionary. It's similar to the argument that opposition equals confirmation -- some religious groups and conspiracy theorists argue that the fact that people oppose them means they are right.
I never said crackpots are guaranteed to be visionaries, though I'm sure it made a convenient strawman for you to argue against. My only point was that you can't be certain either way a priori, to be sure you must actually investigate it (and history tells us even then that's not always going to guarantee certainty).
The depth of investigation should be proportional to the probability of correctness, weighted by the cost of being wrong. Crackpots are called such because the probability of correctness is very low.
Given all the evidence, I consider the MFAP origin hypothesis to be significantly less likely than the primate evolution theory. Extraordinary claims require extraordinary evidence.
to play devil's advocate: consider the extreme absurdity of einstein's theory of relativity, the theory that time may speed up or slow down depending on your velocity.
That doesn't mean that being perceived as a crackpot is a reliable indicator of being a visionary. It's similar to the argument that opposition equals confirmation -- some religious groups and conspiracy theorists argue that the fact that people oppose them means they are right.