I don't think religious people are stupid per se for being religious, but I do think in most cases that they lost a crucial opportunity in childhood to form independant opinions and rational thought.

You make some good points though re trying to reason with religious people. Aside from the deep, deep lifelong programming... there's a little voice in the back of their mind that must be silenced, because it would be incredibly damaging to their psyche to realise they've tied themselves & their lives to something false.