In Chapter 3, Jem invites Walter Cunningham Jr. to their house for supper. Scout makes fun of the way Walter eats his food and she is scolded. Scout replies, "Cal, he's just a Cunningham." Scout probably heard this reasoning from other people in town. Neither Atticus nor Cal would ever say "just a Cunningham." Cal explains that Scout should treat all of her company the same. " Don’t matter who they are, anybody sets foot...
In Chapter 3, Jem invites Walter Cunningham Jr. to their house for supper. Scout makes fun of the way Walter eats his food and she is scolded. Scout replies, "Cal, he's just a Cunningham." Scout probably heard this reasoning from other people in town. Neither Atticus nor Cal would ever say "just a Cunningham." Cal explains that Scout should treat all of her company the same. " Don’t matter who they are, anybody sets foot in this house’s yo‘ comp’ny, and don’t you let me catch you remarkin’ on their ways like you was so high and mighty!" Scout also is surprised to see Atticus talking to Walter Jr. as if they were equals.
In Chapter 12, Cal takes Jem and Scout to her church, the First Purchase African M. E. With the exception of Lula, everyone else is cordial and welcoming. This might have something to do with Atticus being their father, but it also has to do with the Christian notion of the Golden Rule. And in this Christian spirit, race should not matter. When they are confronted by Lula who asks why she's brought white children to a black church, Cal responds "It's the same God, ain't it?"
In a book rampant with inequality, perhaps the most enduring example of treating others with equality is Atticus himself. He is respectful with Walter Jr. at the dinner table. He takes Tom Robinson's case and defends him as well as he can, in spite of a racist jury.
Also, note that Tom had been willing to help Mayella multiple times. In Chapter 19, Tom notes this when he's being questioned by Atticus. The point here is that Tom was willing to help her regardless of race or any still widely held social conventions discouraging a community between whites and blacks. Later in the same chapter, when Tom is being questioned by Mr. Gilmer, Tom says "I felt right sorry for her." This does not necessarily help Tom's case, but he was being honest. He feels sorry for Mayella and that's why he helps her. She certainly did not get any help from her father or her siblings.