Associative reasoning, imo.
The general concept that there is a man in the clouds is absurd to a group of people or entire society that doesn't believe in such things.
But when you want them to believe in it, what better way to get them to accept such a concept than to say "Hey now look.... it has affected this one fellow human here. But he's special because he just so happens to be the son of this invisible cloud dweller we're telling you that you have to believe in. He's his daddy's voice and presence since all living things aren't worthy of it straight from the source. But he loves you despite the fact that he doesn't think you're special enough to talk to let alone be around. So much in fact, that you'll burn for eternity if you're the slightest bit bad and fly like a bird if you're good. Now do what we say, err, what HE says!"?
