In Chapter 20, Dolphus Raymond gives Dill a drink of Coca-Cola from his brown bag and discloses his secret to the children. Dolphus confides in Scout and Dill that he feigns alcoholism in order to avoid conflict with his neighbors for his taboo way of life. Dolphus openly associates with African Americans and even has several biracial children. In the prejudiced community of Maycomb, Dolphus' way of life is scorned. Dolphus refuses to change his lifestyle and feigns alcoholism so that people "can latch onto a reason." Dolphus then attempts to explain Maycomb's prejudice to the children and laments about how the majority of white citizens unfairly treat African Americans. Scout and Dill's conversation with Dolphus Raymond gives further insight into the prominent themes of prejudice, race relations, tolerance, and innocence. Dolphus tries to explain to Scout that her father is different from the prejudiced citizens of Maycomb, but she innocently struggles to comprehend his explanation. Dolphus also discusses how the racist citizens are intolerant to his way of life and comments on how African Americans are unfairly treated. Lee explores these issues in depth throughout the entire novel, and this conversation contributes thematic insights to the story.
In terms of prejudice and tolerance, when Scout and Dill realize that Mr. Raymond isn't really the town drunk (drinking Coca Cola instead), they are shown a new insight into his character. They realize that he is giving the white community the impression he is a drunk because then they will make life so difficult because he prefers to live with African Americans. Indeed he has several bi-racial children. He advises them to not cry over the trial but to cry over the evil people practice upon each other - regardless of race - each and every day. Once we can conquer that evil, then we won't have to worry about racism and intolerance.
This little scene also ties into the role of innocence and experience. There are several examples in the book where Scout has her innocent world view challenged, such as when she sees Atticus shoot the rabid dog, when she sees how Calphurnia acts differently at the black church, when she sees Miss Maudie's attitude after her house has burned down, when she feels sorry of Mayella Ewell during her testimony. This is just another moment in their lives where they realize that the people are not always what they appear to be.