How does Scout get Mr. Cunningham and the mob to leave?
When a group develops a "mob mentality", they become willing to do things they normally wouldn't do if they were in their right frames of mind. This is the mentality of the mob outside the jail. They have allowed their emotions to overtake their reason, and all they want is revenge against Tom Robinson, an innocent black man, whom they think has raped Mayella Ewell.
By talking to Mr. Cunningham, Scout reminds him that he is a father just as Atticus is. She calms Cunningham and the other men down by making them realize that all of them are residents of Maycomb. Scout's innocent remarks turnsthe mob back into a group of friends and neighbors who have always been treated kindly and respectfully by Atticus. As a mob, the men are nameless, but when Scout calls them by their names, the men become individuals.
Scout's childhood innocence makes Mr. Cunningham leave. Here's how: She begins talking to him about his son and his "entailments." She brings out the humanity of Mr. Cunningham. Wanting to instigate a fight, Mr. Cunningham still has enough decency to not do so in front of children. I don't think Scout is aware of what she is doing and how she is diffusing a situation. I do think Jem knows. He is the one who chose to stay when he could tell the danger of the situation.
When Cunningham realizes these children aren't going to leave, and when the mention of his son melts his anger, he and the rest of the mob decide to leave.
Scout, filled with the naivete of her rowdy youth does not quite understand the dangerous situation Atticus faces because of his decision to defend Tom Robinson. She does not understand the racial injustices that occur daily and why the African-American community should be forced to suffer in the misery of prejudice. Without thinking, she prances into the scene and warmly greets Mr. Cunningham: believing they have gathered on good terms. She speaks to the mob as if they are friends and speaks to Mr. Cunningham, who she notices to be uncomfortable, about his son and how kind he is. She feels sympathetic towards him and attempts to bring good cheer to him by speaking well of his son.
The mention of Mr. Cunningham's son arouses not only in Mr. Cunningham but the majority of the mob, empathy: empathy towards Atticus. They are reminded of their own children and how they would feel if in a similar situation and cannot bear the guilt of having to start such violence in front of the innocent Scout. Scout begins to name the individuals within the mob, bringing out once again the thoughts of the individuals and separating the once mindless, savage and animal-like group of men with only one evil goal in mind.
scout shoots them all with a 2 gauge shotgun