Atticus Finch is about as dignified as a character as you'll ever see in American Literature. Atticus defends Tom to the best of his ability even though many people in the town think he shouldn't. Atticus does the right thing no matter what. At one point he tells Scout that if he didn't defend Tom, he wouldn't be able to tell Scout and Jem not to something again.
The answers are related, but distinct. Lee portrays it as everyone's responsibility to fight for human dignity, and indicates that the battle can be fought everywhere and anywhere; human dignity is generated through moral courage and depends on that quality. Whether it is Calpurnia protecting the children at her church or Atticus defending Tom, characters attain dignity not through winning their battles but through standing up for what they know to be right.