It's been a puzzlement for many of us. What could possibly reduce an essentially good person to behaving the way they do? I think I know, but it wouldn't be very tactful to post it, and it wouldn't change things anyway.
"What could possibly reduce an essentially good person to behaving the way they do?"
Fear. They are afraid of going to H E double hockey sticks, of losing their friends in church, of going against the authority of their pastor, of having their wife leave them if they don't believe in the literal Word etc.
A lot of it is cognitive dissonance caused by fear. Fear is a key factor in a lot of mental illness. The sad thing is that for Christians, Jesus alleviates fear through love and gives us peace in all circumstances. This is why Christian belief often heals mental illness.