'Pears that they think that anyone who's not one of them is a potential pedophile/rapist/angel of darkness.The(ir) "One True God[tm]" is the one source of morality. If you don't believe in Him (the right way and based on the right translation of what He said) then what restrains you from the most wicked acts of depravity?
This suggests of course that if that person has a crisis of faith they will go all Lord of the Flies on you.