[modo_mario]

Religion is ultimately for a great part a matter of identity and they sure don't think of themselves as retards.

People think it's doctrine, scripture and proseltysing that sustains it and anyone looking into those first 2 at least would think they're idiots but mostly it's things like CREDs (credibility enhancing displays) and group ties that contribute to believers selfidentity which calcifies the belief.

Looking at their or a different religion for what it is would challenge their sense of self and as humans we really don't like that kind of cognitive dissonance.