How we cite our quotes: (Part.Chapter.Paragraph)
Quote #4
"It was white folks you like so much that tried to cut your brother's throat.
[ . . .]
"And he was trying to cut theirs. Him and them bad boys." (1.1.165-67)
Gabriel takes Roy's wound to be evidence that supports his hatred of all white people; he wants John to see it, to understand that he should fear white people because of their violence. Florence, though, reminds everyone that Roy himself was also participating in the violence, and that the issue isn't so…ahem…black and white.
Quote #5
"You slap me," she said, with a placidity equally fearful, and I do guarantee you won't do more slapping in a hurry." (1.1.170)
When Gabriel threatens his sister, Florence, she lets him know that she is not a good option for his violent urges. By threatening him with further violence, even if she isn't really capable of beating him up, she is setting a boundary that he knows he shouldn't cross. Unfortunately, he just turns his violent attention elsewhere.
Quote #6
Then, with all his might, he reached out and slapped her across the face. She crumpled at once, hiding her face with one thin hand, and Aunt Florence moved to help her up. (1.1.186)
Gabriel is so angry about Roy's injury that he looks for someone to blame. First it's the white people who cut his son, but since they're not there to beat up on, he turns to his wife. He accuses her of carelessness, saying that it's her fault that their son has been hurt. Rather than see her as his partner he turns her into an enemy and slaps her.