How did Scout diffuse the passion of the gang?
In Chapter 15, Mr. Walter Cunningham and a bunch of his friends have all come to the jail to try to lynch Tom Robinson before his trial. They are starting to threaten Atticus to try to get him out of the way when Jem and Scout get there. Scout diffuses the passion of the gang without even knowing that she is doing it.
She sees Mr. Cunningham and knows that she should be polite to him so she starts talking to him about his legal issues (his entailment). Once she starts talking to him about that and his son, she gets him to start relating to her as a person. He and the rest of the gang sort of wake up to what they're doing and then disperse. So what she's done is she's made him start to think like a person instead of like mindless member of a mob.