Few people are the same as they are on the street in their homes. Few people can treat others equally; no matter what colour their skin is. Atticus Finch is one of those precious few. Racism in the town of Maycomb is nothing but disguised by the polite smiles and ladies missionary meetings; although it is the strongest belief that each person of the town holds apart from some such as Atticus. Racism is an issue of great importance, yet to the eye of a visitor waltzing through, it's just a slight whisk of air.
Atticus is a good man, a just man. He upholds his morals, and judges by his conscience. He is shaken but not moved by the town of Maycomb in their gossip and hypocritical ways. When offered Tom's case, Atticus knows he will take it on. He won't just stand there with no proper defense for Tom, but he will let the truth be known, and prove that Tom is innocent. "...that boy might go to the chair, but he's not going till the truth's told."
If Atticus didn't take on the case, he couldn't hold his head up in town; couldn't represent this country in the legislature; couldn't even tell Scout or Jem not to do something again'. "...before I can live with other folks I've got to live with myself. The one thing that doesn't abide by majority rule is a person's conscience."
Atticus has a clear mind. He will not sit by and watch as his two children are abused and their views twisted to match the society of racism they live amongst. Atticus builds his morals up in the children very evidently, although no so much as to draw attention. He speaks words of wisdom to them in their distress, but also with the treatment and position of Calpurnia, he is able to demonstrate a precise view of his own conscience. Atticus knows that because of this, he is considered one of the most non-racist people in Maycomb, therefore being offered Tom's case. Judge Taylor knows the right man for the job.
Before he even begins, Atticus knows the case is already lost. They were licked a hundred years before it even started, but still he fights for innocence.