Why did francis and scout get in a fight on Christmas day?

Francis called Atticus, Scout's father, a black-lover. Scout forgets everything Atticus had told her(to ignore people's comments on him and lower her pride and not get into fights) and loses her temper and fights with Francis. Later on, she gets into trouble but Uncle Jack hears her side of the story and finds out that Francis is the trouble-maker and he is the one that starts every fight. (: