From the original post:

People who grow up believing certain things,
even if they later stop believing them,
may not quite realize how the beliefs sound to outsiders...

I dare say, the real horror of this realization is unknown to you unless you have had it about some belief that is seen in your culture as so fundamental to common sense and moral propriety that only lunatics and utter monsters could ever believe otherwise.

And no, in Western societies traditional religion doesn't qualify here, unless perhaps you come from some very extreme and isolated fringe religious group.