Our brains make judgments, before we even have time to process their face. In the story of Angus Bethune, people like Rick automatically assumed that he was bad because he was fat. We need to look past this to see how they really are.
By judging others we blind ourselves to our own evil and to the grace which others are just as entitled to as we are. This is a quote by Dietrich Bonhoeffer, and it is saying that if we judge, then we are just as bad as our perceived perspective of the person we are judging.
The idiom don't judge a book by its cover means that even if someone is ugly or fat on the outside, like Angus, you shouldn't judge him.
In this scripture it famously said, "Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye." This is saying that until you can become perfect yourself, don't judge others
Bob Marley is making a great point, not to judge people, because you don't always know the full truth.
In the story Angus Bethune, people judge him, and think he's bad because he is fat. A theme is Don't judge people for what they seem to be.