What faults and problems in the legal system are revealed in the conversation between Atticus and Jem?

Atticus comments that too many people are sent to death based upon purely circumstantial evidence. Jem thinks that juries should be done away with, because they can't make reasonable decisions. Atticus responds that men don't behave rationally in some situations, and will always take a white man's word over a black man's. Atticus tells Jem that any white man who cheats a black man is trash.