But fundamentally his beliefs are no different! There is not a shred of evidence in favour of his beliefs over Great Uncle McCrazy (GUmC henceforth). You're correct that we should judge him purely based on his actions as a human being. However, these actions are based on his beliefs, and we can criticize these actions
as being immoral (homophobia, being an example that greatly annoys me). Yet he gets accorded respect because of his position as a head believer of [the purple dinosaur] regardless of his homophobia and promotion of actions that cause harm (non-use of barrier contraception).
Summary: We can't criticise someones beliefs rationally directly
, but we can certainly criticise immoral actions made because of them. And you can't give someone respect for believing strongly in something that's unprovable, because if we did then lunatics (actual lunatics, I mean crazy people here) would be in charge of society - due to their unshakeable belief in concepts not provable in reality.
And as for the whole slashdotter science fiction angle that you're worked up about, sure they can't disprove the existence of god. But remember, they can't disprove the claims of Great Auntie McCrazy that somewhere out there are invisible alien beings watching
over the universe.