Could you please explain the following quote in To Kill a Mockingbird?
"...without catching Maycomb's usual disease. Why reasonable people go stark raving mad when anything involving a Negro comes up..."
In this passage Atticus talks with his brother after their Christmas meal; his brother Jack expresses his conern with Atticus's acting as defense attorney of Tom Robinson because he fears the impact of the trial on Jem and Scout. But, Atticus declares that his conscience will not allow him to do so, telling Jack that he hopes to get his children through the trial without their catching "Maycomb's usual disease" of racial prejudice which will prevail in the court trial of Tom Robinson. Atticus here alludes to the things that people do to further their beliefs in racial inequality.
These activities of the "disease" of racism are illustrated in the mob scene as they "go stark raving mad," and in the gathering of the men in the front yard of the Finches' home. The hatred that will permeate the environment is something Atticus hopes his children can avoid, and something about which Uncle Jack is apprehensive. Nevertheless, his integrity will not allow him to shelter his children or to refuse the case as he must be faithful to his unwritten moral code of fairness to all, "considering their point of view."
mwestwood's reply is very good.
I want to add that this quotation from Harper Lee's novel To Kill a Mockingbird helps me, as a reader, make sense of the scene involving the rabid dog toward the end of part one of the novel. Just as rabies can turn a friendly animal into an almost unrecognizable and dangerous threat, the racism in the community can send otherwise normal people into a mob that is "stark, raving mad."
In both instances -- in the scene with the rabid dog and in the trial scene -- all hopes to combat the irrational and destructive force of rabies/racism are put not on the sherrif but on Atticus and his deadly aim. He manages to kill the dog with one shot, but he does not experience a similar success with the jury, of course.