Harper Lee's To Kill a Mockingbird examines life in the small Southern town of Maycomb. During the time described by Lee, persons of color were treated as second-class citizens by those with light-colored skin.
"Black" people stereotypically held menial jobs such as housekeeper (e.g., Calpurnia; Aunt Alexandra's chauffeur). In the courtroom, the persons of color are relegated to the balcony.
The mere dark color of their skin renders them as untrustworthy in the eyes of their white counterparts, as evidenced by Atticus' remark, "The only thing we’ve got is a black man’s word against the Ewells' (Chapter 9). Thus, Tom Robinson is assumed to be guilty before the trial even starts. After all, as Atticus tells the court in his summation in Chapter 20, the common belief is
"that all Negroes lie, that all Negroes are basically immoral beings, that all Negro men are not to be trusted around our women".
Unfortunately, the jury cannot escape the prejudice that they hold and believe the logical defense that Atticus provides for Mr. Robinson. Even the white school teacher, Miss Gates, supposedly an educated person, cannot see that Hitler's treatment of the Jews is not much different than the way the white folks of Maycomb treat people of color. It takes young Scout to realize the incongruity in the situation:
Jem, how can you hate Hitler so bad an‘ then turn around and be ugly
about folks right at home—”