What does Cousin Francis do that infuriates Scout?

A conversation about Dill Scout's friendship (including his marriage proposal) turns into a mean-spirited attack on Atticus. We know Scout isn't going to tolerate that!

“If Uncle Atticus lets you run around with stray dogs, that’s his own business, like Grandma says, so it ain’t your fault. I guess it ain’t your fault if Uncle Atticus is a nigger-lover besides, but I’m here to tell you it certainly does mortify the rest of the family—” “Francis, what the hell do you mean?” “Just what I said. Grandma says it’s bad enough he lets you all run wild, but now he’s turned out a nigger-lover we’ll never be able to walk the streets of Maycomb agin. He’s ruinin‘ the family, that’s what he’s doin’.” Francis rose and sprinted down the catwalk to the old kitchen. At a safe distance he called, “He’s nothin‘ but a nigger-lover!”