In Harper Lee's To Kill a Mockingbird, Atticus teaches Scout that using the word nigger is offensive and beneath her dignity.
In Chapter 9, Scout begins being persecuted by kids at school for her father's decision to defend Tom Robinson. When Cecil Jacobs makes Scout feel insulted by saying her "daddy defend[s] niggers," Scout attacks him even though she's not really sure what he means. She asks Jem what Cecil means the first chance she gets, who tells her to ask Atticus, leading Scout to next ask, "Do you defend niggers, Atticus?" Atticus replies that he certainly does but further says, "Don't say nigger, Scout. That's common."
One definition of common refers to anything that is "of mediocre or inferior quality; mean; low," meaning anything that is base, inferior, offensive, or tasteless (Random House Dictionary, 2016). Therefore, in telling Scout the word nigger is common, Atticus is saying that using the word is beneath her. He is saying that the rest of society uses the word because they are inferior people who want to be offensive by treating African Americans as inferior. In contrast, through his actions, Atticus teaches his children that all people, though not born with equal advantages and opportunities, deserve to be treated with equal respect. He treats Calpurnia with respect by calling her a "faithful member of this family" (Ch. 14), and he treats Robinson with respect by putting his all into defending Robinson in trial.