When Atticus's sister Aunt Alexandra comes to town, she and Scout are almost immediately at cross-purposes over Scout's clothing (overalls) and tomboylike behavior which to her mind does not fit well with the Finches' "place" in the upper level of social hierarchy of Maycomb County, a place they earned simply because their family has been in the area for a long time. The so-called "good" families are generally white and are descended from well-to-do Southern whites, like Simon Finch, Scout's ancestor who owned and ran a successful Alabama plantation prior to the Civil War.
Atticus does not have much interest in the family's "good family" status, and were it not for Alexandra, the reader would not even be aware of it because Atticus doesn't care to discuss it. After one particularly unhappy conversation, when Atticus was supposed to be discussing the family's superiority with Jem and Scout, he gets flustered at their intelligent questions about the silly business, gives up and tells them to forget about it. His frustration is not with them during this conversation, but with what he perceives to be their fair questions, and his belief deep down that they are right and that the whole "good family" thing is nonesense.
Atticus's moral philosophy of tolerance and equality among men is nowhere more apparent than when he gives Tom Robinson the best defense he can, despite the disapproval of the townspeople: at trial, he shows everyone in the room that there was no possible way Robinson could have committed the crime he was accused of; predictably, Robinson, a black man, is found guilty because the accusation was leveled by a man, who, disgusting and despicable, was also white. Atticus knew he was beaten before he started, but he made sure that Scout and Jem knew that he was still obligated by conscience to try his best. The black community knew it, too; while Atticus couldn't get Tom Robinson a not guilty verdict, he planted enough doubt in their minds that they were out deliberating far longer than anyone thought they would be. In fact, Miss Maudie commented on this phenomenon to Scout and Jem, who were heartbroken about the verdict, saying, "I thought, Atticus Finch won't win, he can't win, but he's the only man in these parts who can keep a jury out so long on a case like that."