To Kill a Mockingbird takes a stand against social exclusion on several levels. Social exclusion can be defined as the marginalization of people based on economic, political, religious, or cultural differences or affiliations. It can happen on a small scale, as in the social sphere of family; a medium scale, such as on a community level; or a large scale, such as a national ideology.
In this novel, the social marginalization that is rooted in racism is enmeshed in the very fabric of the community. It is behind the segregation of groups in social settings. For instance, when Calpurnia takes the Finch children to her all-black church, one woman does not accept them, and if the children are accepted in this setting, it seems to be because Atticus is their dad—he is representing Tom Robinson, which gives him an "in" with the black community.
Social marginalization also determines what jobs people can and cannot have. Most of the black people in the novel have labor- or service-related jobs; most, like Calpurnia, are not formally educated. Social marginalization also strongly influences how people treat one another. When Atticus takes the Tom Robinson case, his children are bullied by members of their own community, by both children and adults.
Experiencing social exclusion means being an outsider. The "contrary" affiliations that marginalized people have that qualify them to be ostracized is often viewed as a threat to society. Whether political, economic, religious, or cultural, these differences are perceived as a threat to the "norm."
For example, Mr. Dolphus Raymond experiences social marginalization because he is in an interracial marriage. His love for a black woman is a threat to the "norm" of social segregation that permeates all aspects of life. Mixing races therefore threatens a societal structure that is rooted in racism; if the races mix, then who can be educated? Where will people go to church? How does one treat a child with both white and black blood, since one is supposedly superior?
When almost everyone is gathered in the courthouse, Mr. Raymond must remain outside. He knows he is not welcome. His white community treats him—and speaks of him—as if he is an evil man. Scout thinks that he is an alcoholic because he carries around a brown bag that he drinks from. However, she eventually finds out it is not liquor, but Coca-Cola. When she asks Mr. Raymond why he pretends to be a drunk, he says:
Some folks don't—like the way I live. Now I could say to hell with 'em. I don't care if they don't like it. I do say I don't care if they don't like it right enough—but I don't say to hell with em, see? . . . I try to give 'em a reason, you see. It helps if they can latch onto a reason. When I come to town, which is seldom, if I weave a little and drink out of this sack, folks can say Dolphus Raymond's in the clutches of whiskey—that's why he won't change his ways. He can't help himself, that's why he lives the way he does . . . It ain't honest but it's mighty helpful to folks. Secretly, Miss Finch, I'm not much of a drinker, but you see they could never, never understand that I live like I do because that's the way I want to live.
In this excerpt, the novel is taking a stand against social marginalization. Mr. Dolphus Raymond is shown to be exceptionally understanding of why society has rejected him. He knows that the white community is so indoctrinated to a racist perspective that some things are beyond their comprehension—such as how he fell in love with a black woman and chose to build a family with her. He also shows himself to be merciful to those who exclude him, in that he pretends to be an alcoholic so they can rationalize his choice. He does not wish to "shake-up" the worldview that is so integral to how their society functions.
Atticus, on the other hand, does take a stand that "shakes-up" people's worldview. By giving a black man fair representation in court, he is also threatening the societal norm which inherently assumes the guilt of black men—most especially when against the word of a white person.