It is the trope of "climb[ing] into his skin and walk[ing] around in it" that best illustrates the development of compassion on the part of the Finches for African-Americans (as well as others) in To Kill a Mockingbird.
Until the trial of Tom Robinson, Scout and Jem's experience of the world has solely been their neighborhood or school (which was, of course, segregated in the setting of the 1930s). Therefore, their only contact with black people has been Calpurnia, the maid who acts also as a substitute mother to the children. Despite Scout's little bouts of peevishness, she loves Calpurnia and realizes how much Calpurnia loves her after her first day of school when the woman bends down and kisses Scout (Ch.3). That Calpurnia is an integral part of the Finch family becomes very clear after Aunt Alexandra arrives and tries to become a matriarch. She forbids Calpurnia to bake the tea cake for her meeting with the prestigious ladies of Maycomb; she urges Atticus to let her go as though she were some mere employee. But Atticus defines Calpurnia as a "faithful member of this family" (Ch. 13). Then, when Calpurnia takes the children to church one Sunday, Scout and Jem are made aware of the two entirely different worlds in which Calpurnia exists. While Aunt Alexandra is peeved that the children went to church with the maid, Atticus thinks the exposure was good for his children as they now realize the poor conditions in which many of this community live.
- Reverend Sykes and his church
During their visit to Calpurnia's church, the children are treated graciously by most of the members, but they do experience racial bias against them, an experience which touches the emotional understanding of the children when they witness the attitudes toward the innocent and charitable Tom Robinson. Reverend Sykes calls upon the charity of his congregation to help Helen Robinson, furthering the apprehension of the children about the conditions of life for African-Americans in Maycomb. Later, at the trial, Scout and Jem readily accept a seat beside the kindly Rev. Sykes in the balcony, unaware of the designation of such a balcony for black people only because their father has never mentioned such a thing.
- Mr. Dolphus Raymond
During the questioning of Tom Robinson, the solicitor Mr. Gilmer is insinuating and antagonistic toward Tom. When Tom lets it slip that he "felt sorry" for Mayella, Mr. Gilmer allows a long time for this answer to register with the audience. He then addresses Tom as "boy" and is very hostile toward Tom. Scout finds herself taking an emotional Dill outside. Dill cries because Mr. Gilmer speaks so cruelly to Tom. "It was the way he said it made me sick, plain sick," Dill tells her. Scout replies that Gilmer is just doing his job, but Dill counters that Gilmer did not talk that way to the other witnesses. Dill points to how the solicitor has called him "boy" and looked around at the jury every time Tom speaks. Scout ingenuously comments, "Well, Dill, after all he's just a Negro," because she simply reflects the status quo. However, Mr. Raymond overhears and says, "I know what you mean....You aren't thin-hided, it just makes you sick, doesn't it?"
After Scout and the other children get to know Mr. Raymond and realize that he merely pretends to be a drunkard, they grow in their understanding of social prejudice which marginalizes Mr. Raymond because of his association with the African Americans. Raymond, who is more understanding than the other citizens, explains that he pretends to be a drunkard so "they have a reason" to scorn him.
- Atticus Finch
Atticus is an extremely liberal-minded man in all ways (no other children would call their father by his first name as even today many Southern children answer with "sir" and "ma'am" to their parents and refer to them as "Mama" and "Daddy" even as adults). As this liberal man, Atticus earns respect more than he demands it. He reasons with his intelligent children and they draw logical conclusions, although they may stumble some along the way. Then, he allows them to learn from their mistakes and to form their own judgments.
Certainly, he sets a stellar example of decency and fairness to all people regardless of the cost. He refuses to give the task of defender to anyone else, saying that he does not want his children to catch "Maycomb's disease" and he wants them to respect him. He protects Tom at the jailhouse despite the threat of the Old Sarum Bunch; he stands up to the men in the front yard who want the trial moved from Maycomb, and he does everything he can to defend Tom Robinson against the indefensible testimony of the--to paraphrase Zora Neale Hurston--"tragically" white reprobate Bob Ewell.
This is a good question. The whole thrust of the book shows that some people have compassion and others do not. For example, Bob Ewell could care less. However, people like Atticus care deeply about the African American community. The proof of this is that he takes on Tom Robinson's case, even though he knew he was going to lose.
Also Atticus employs Calpurnia and gives her great respect. He trusts Calpurnia with his children completely. This shows that he extends trust. Even when Alexandra questions this, Atticus stands firm.
Within this family context, it is no surprise that Scout and Jem also treat blacks well. They have a heart to protect and love all people. So, when Tom Robinson loses in court, both Jem and Scout accept the verdict with great difficulty. They saw something unjust.
As for Haper Lee, she grew up in a time of racism. So, her book is a tribute to her desire to stand for what is right.