Atticus deviates from the stereotypical prejudicial behavior of the white old south in many ways. First of all, he defends Tom Robinson. And while he was appointed to do so, it was always his option not to defend Tom as he should have. That is, he could have written Tom off as a "lost cause," or defended him with less enthusiasm because of his color, but Atticus defended him just as if he were anyone else; black or white, it made no difference. This display of colorblind objectivity is one way that Atticus defies the prejudice of his setting.
Atticus Finch is the epitome of passive resistance throughout the course of the novel. The only time his feathers seem to be ruffled is when he learns that his children were attacked by Bob Ewell. He is a strong, stoic figure, who faces the problems of the novel with a quiet intelligence. He does not fight with his fists, but with his words. He tells his children to not engage, particularly rambunctious Scout, in any sort of fight, even when children call their father "n-- lover" and make fun of them for their father's defense of Tom Robinson. When Bob Ewell spits in Atticus' face, Atticus simply wipes away the spit and calmly states "I wish Bob Ewell didn't chew tobacco." When facing the angry lynch mob coming for Tom, Atticus stands firm, no harsh words nor aggresive heroic gestures.