Atticus Finch protests against Jim Crow by not allowing his children to refer to the African-American members of the community using the pejorative term that others do, and by treating Calpurnia as a member of his family.
In Chapter 9, when Scout comes home after Cecil Jacobs has made an announcement in the schoolyard that Atticus Finch defends n*****s, she asks her father if he does, and Atticus affirms that he defends them. But, he instructs Scout to not use this pejorative term for black people because it makes a person seem "common" (low class).
Then, in Chapter 14, after his sister Alexandra has come to stay with Atticus and his family, the brother and sister have an argument over Atticus's employment of Calpurnia. Aunt Alexandra tells Atticus that Calpurnia is no longer needed; however, in an "even" tone, Atticus replies,
"Alexandra, Calpurnia's not leaving this house until she wants to....She's a faithful member of this family and you'll simply have to accept things the way they are."
Atticus not only gives Calpurnia equal standing in his home, but he speaks of her as a family member. He praises her as being stricter with the children than a mother would have been, and argues that she raises the children with a sound set of ethics. Moreover, there is love shared among the children and Calpurnia. After Atticus's words, Alexandra is "furious" because her brother has gone against he conventional wisdom of their culture.