When Jack asks about the Tom Robinson trial, Atticus responds by saying that he plans to present the best defense possible. Many people in Maycomb don't like the fact that Atticus intends to defend a black man with honor and honesty; but, he doesn't care what others think. What is more important to Atticus is that he stands up for what is right and that he is a good example for his children. For instance, Atticus believes that everyone should be granted a fair trial--even though life outside of court isn't fair. Unfortunately, because of the racial prejudices that have existed in Maycomb for generations, many white people don't agree with him. Atticus tells his brother the following:
"You know what's going to happen as well as I do, Jack, and I hope and pray I can get Jem and Scout through it without bitterness, and most of all, without catching Maycomb's usual disease. Why reasonable people go stark raving mad when anything involving a Negro comes up, is something I don't pretend to understand . . . I just hope that Jem and Scout come to me for their answers instead of listening to the town" (88).
Maycomb's disease is not only racism or bitterness but the fact that white people become upset when the status quo is challenged. For years after the Civil War, white people have treated black people like second-hand citizens. They don't believe that blacks should have a fair trial, or own land, or vote, for example. Therefore, the disease that Atticus is talking about can be witnessed whenever white people in Maycomb encounter any situation that involves both black and white people. It seems as though whites refer to their prejudices to guide their behavior rather than referring to love, justice, or common sense. Atticus does not want Jem and Scout to adopt the prejudiced habits that seem to surface whenever there is an interracial situation in Maycomb.
Atticus hopes that Jem and Scout will go to him for the answers they seek and not become prejudiced or irrational when situations arise between white and black people. Fortunately, his hopes are realized. Since Atticus has a good relationship with his children, they are not afraid to ask him the difficult questions when racial tensions rise before, during, and after the trial.
The "disease" is a kind of madness—a loss of reason when any legal issue involving Blacks occurs. He hopes that they'll come to him for sensible answers instead of listening to the gossip. (His insistence on them thinking for themselves, reading, and doing the right thing should have laid the groundwork for this.)