They always get very angry when they hear the words from a book that they don't even believe in. If God isn't real to them, why would a bunch of stories about a fictional character bother them so much? It bothers them because deep down they know they are doing things that are wrong and that God will indeed judge them. If they truly believed there is no God and no consequences, they'd just laugh at people who preach to them like this. Their reactions reflect the real truth here.