You shouldn't tell others information that seems impossible.
Don is talking about religion with his friend, and his friend asked him why he believes in God.
Don wants to explain why he believes in God.
Don tells his friend that his family used to read him bible verses all the time.
Don tells his friend that God spoke to him when he was younger.
Don's friend understands his explanation and doesn't look down on him.
Don's friend will think that Don is crazy and will think that he's a liar.