Atticus challenges social injustice and prejudice by defending Tom just as he would any other person. Can you imagine the pain and suffering he must have endured as a white man defending a black man? Can you imagine how difficult he must have known the trial was going to be because despite giving a sound case, Tom was already guilty because of the color of his skin? I think Atticus is a brave man and one who definitely stood out in his day.
Atticus also had the courage to teach his daughter about prejudice. He could have gone about his work and defended Tom without taking the opportunity to teach his daughter about the evils of the world. By doing so, he made a statement about how future generations should react to such injustice.
He stood up for what was right not only the day of the trial but also ensured that future generations might consider their prejudices by teaching his daughter about his beliefs. Atticus was a brave man. I couldn't help but think how much he must have been ridiculed for standing up for Tom. I can't help but think how much his career must have suffered because he had the guts to stand up.
Atticus rejects the social codes of the day by really trying to give Tom Robinson a vigorous defense. He realized that he would probably lose in court because the social codes of the day dictated that a black man accused of raping a white woman would invariably be found guilty. But he laid the foundations for proving Robinson's innocence on appeal. Unfortunately, Tom did not trust the courts enough and dies in an escape attempt before Atticus can file the appeal. The second instance of Atticus rejecting the social codes is when Jem brings Walter Cunningham home for lunch. Atticus treats Walter, who is poor and at the bottom of the social ladder, with just as much respect as he would any guest in his home. When Walter insists on pouring syrup over his meal, Atticus simply treats this as normal, much to Scout's surprise.