Scout is observing how Atticus, a reasonable and empathetic man, cannot hope to prevail with racist men and their ignorant, stubborn beliefs. This is a theme that is developed in more detail following the trial. In chapter 23 Jem is frustrated by the jury's refusal to dismiss the charges against Tom, even though he was clearly innocent. Atticus knew this would happen and tried to prepare Scout and Jem for it. That is why he had to walk a fine line - and that is one reason for having Jem read to Miss Dubose - Atticus wanted the kids to realize that why Maycomb's residents might be stubborn and ignorant in their beliefs, they were still their neighbors and friends.