Why should'nt Atticus defend Tom Robinson? To kill a mocking bird

Atticus has a lot to lose. Defending a black man against a white community bent on revenge, regardless of the truth of the situation, is a futile battle. Maycomb is a small town with strict racial codes of belief. Atticus puts his livelihood, his safety, his reputation and even the well being of his family on the line. Atticus, however is a man who does the right thing and shows his children what it means to be a human being. Sometimes one must risk everything for truth, justice, and compassion.