In "Night of the Living Rez," what is David's rhetorical purpose in describing the details of how his mother is driving as she questions him about his father?

David's mother runs a red light and then later swerves the car as she puts out a cigarette, which shows that she is not a careful driver, even with David in the car. David offers these details to point out the irony in his mother implying that his father might not be careful with David. He does not tell her about his father falling asleep at the wheel, because he sees no point in it, perhaps because his mother and father are more alike than his mother would admit.