What does Scout learn about mob mentaliy

What is the name of the story or book?

This happens in the general consensus among the white population that a black man, Tom Robinson, could not be telling the truth over a white man's word, even if that white man is Tom Robinson. A direct example is the mob of men who threaten Atticus in front of the jail house. It takes the innocence of a child, Scout, to diffuse the situation. Scout learns that mob mentality is blind and ignorant. She also learns that they are still people and there is humanity to appeal to if one can find it.