Harper Lee set To Kill a Mockingbird in the segregated South during the 1930s, so it is not surprising that she addresses the issue of racial prejudice in this novel. The most egregious example is seen in the justice system during Tom Robinson's trial; however, three white men (the sheriff, the judge, and his lawyer, Atticus Finch) all strive for justice because it is the right thing to do.
The characters are black and white, rich and poor, mean-spirited and kind, educated and illiterate, and everything in between; both the "good" and the "bad" characters come from each of these groups. Harper Lee uses this interesting mix of characters to make the point that race has little or nothing to do with the way a person chooses to act toward others and racism is practiced by many kinds of people.
The Cunninghams are an exceptionally poor white family; however, young Walter Cunningham has a knowledgeable conversation with Atticus over lunch one day, Walter's father faithfully pays for Atticus's legal help with whatever he has and changes his mind about wanting to lynch Tom at the jail. In fact, Walter's father is a member of Tom's jury, and it is likely that he is the one who kept the jury out for as long as it was.
The Ewells are also an exceptionally poor family. Mayella does her best to care for all her younger siblings, and she yearns to be loved by someone who will be kind to her. Unfortunately, she is misguided in choosing Tom and only accuses him of raping at her father's insistence. Bob Ewell, on the other hand, is Mayella's mean, vindictive, and immoral father. He treats the court with disdain by lying about Tom, and it is clear that he mistreats Mayella. He tries to kill Jem and Scout simply because their father exposed him as a foolish racist during Tom's trial.
The Robinsons are black, but both Tom and his wife are kind people who do their best to treat everyone they meet with dignity and respect. Tom kindly offers his help to Mayella when she asks him, which eventually costs him his life.
On the other hand, Lula is a black woman who is angry with Calpurnia for bringing Jem and Scout to church with her. Lula said, “You ain’t got no business bringin‘ white chillun here—they got their church, we got our’n. It is our church, ain’t it, Miss Cal?” Lula is quickly ushered out of the service after this outburst, but it is clear she is a mean-spirited, prejudiced woman. And she is black.
Many characters, such as Link Deas, have suffered the effects of racial prejudice; others, like B.B. Underwood, despises blacks but is outraged when they are mistreated. Miss Maudie is a white woman who believes in justice and equality; however, she is routinely scorned by the "foot-washin' Baptists" for enjoying her garden. Miss Stephanie Crawford is also a white woman, but she is a gossip and a storyteller.
Calpurnia, Atticus's housekeeper, learned to read from law books given to her by Atticus's grandfather; virtually no one in Calpurnia's church can read at all, so they sing their hymns with a method called "linin'."
The point Harper Lee makes about racism is the same point she makes about gender, social class, education, religion, and temperament. While it is true that racism is still the habit and practice of the South as seen in this novel, her characters do not always fit into neat and comfortable stereotypes.
Harper Lee's message, then, seems to be that racial prejudice is a foolish practice, no matter who does it.