It’s the same argument of why some Christians are terrified of atheists.

To them, the only thing that stops someone from raping, murdering, and stealing their way through life is the book they had shoved down their throat in Sunday school. They can’t envision a world where people just have morals all on their own, it has to come from an external source like religion. So someone without that external moral compass must be deranged and dangerous in their eyes.

Of course, to a normal person, this view itself is utterly deranged, and speaks more about the religious person’s complete lack of inherent morals. If the only thing stopping you from raping, murdering, and pillaging your way through life is some old book and some stories about a cool dude, then you’re not really a good or trustworthy person. Especially since that same book says you can do all those terrible things, and as long as you go “sorry teehee” right before you kick the bucket, you get to go to the McDonald playplace in the sky anyway.