How we cite our quotes: (chapter.paragraph)
Quote #1
"There's some folks who don't eat like us," she whispered fiercely, "but you ain't called on to contradict 'em at the table when they don't. That boy's yo' comp'ny and if he wants to eat up the table cloth you let him, you hear?"
"He ain't company, Cal, he's just a Cunningham-"
"Hush your mouth! 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! Yo' folks might be better'n the Cunninghams but it don't count for nothin' the way you're disgracin' 'em—if you can't act fit to eat at the table you can just set here and eat in the kitchen!"
Calpurnia sent me through the swinging door to the diningroom with a stinging smack. (3.26-29)
Cal's moral lesson here is to respect people's differences, even if you think you're better than them. And acting like you're better than other people is the surest way to show that you're not. This interaction is an early blow against the stereotype that white people have morals but African-Americans don't—and Cal follows it up with a loving "blow" of her own. There's nothing like a smack to make a lesson hit home, right?
Quote #2
"There are just some kind of men who—who're so busy worrying about the next world they've never learned to live in this one, and you can look down the street and see the results." (5.44)
Miss Maudie's talking about Nathan Radley here, but also about his fellow foot-washing Baptists who think she's going to hell for making her garden pretty. Miss Maudie's no party girl, but she still strikes out at those who think that all pleasure is bad—except for the pleasure they obviously take in judging their neighbors as sinners.
Quote #3
"If you shouldn't be defendin' him, then why are you doin' it?"
"For a number of reasons," said Atticus. "The main one is, if I didn't I couldn't hold up my head in town, I couldn't represent this county in the legislature, I couldn't even tell you or Jem not to do something again." […]
"Atticus, are we going to win it?"
"No, honey."
"Then why-"
"Simply because we were licked a hundred years before we started is no reason for us not to try to win," Atticus said. (9.16-25)
For Atticus, you have to judge yourself before you can judge anyone else. Or something like that. His own self-respect is bound up with his good morals: if he did something he knew was wrong, even if it was justified, he would lose all moral authority over others.