Refuse is strong language for something so trivial, in my opinion. Although, I will say, your opinion makes sense to me!

To play devil's advocate: I've always thought Indy didn't believe in any of that mumbo jumbo in Temple either and chalked it up to a placebo effect on the believers when the relics worked in his favor. Also, technically, he didn't disregard the ark's power in the end -- right? He made sure his eyes, and Marion's, were closed when Belloq opened the ark. Could've been putting on a front to keep the government out of his way as much as possible.