Ross is perfectly capable of reasoning within both frameworks. He doesn’t have to sort out which one is “true”. Some people don’t worry much about truth. Science, to them, is a game with rules. So is religion. Ross plays one game by its set of rules, and the other game by its other set of rules.
He’s not insane, because what he’s doing works for him and anybody who consistently reaps an advantage from his behavior can only be crazy as in `crazy like a fox’.
What’s crazy is listening to him and believing that he sincerely believes any of what he says.