How do Cal and Atticus challenge Scout's behaviour towards Walter in To Kill a Mockingbird?
Cal and Atticus both treat Walter with great respect, like they would anyone else, and Scout learns that lesson from both of them in different ways. When Walter comes with Scout to lunch at home, Scout comments in a negative way about Walter's manners, to which Calpurnia sternly admonishes her that Walter is a guest, who will be treated with respect by everyone in the Finch household, including Scout herself. In a separate situation, Atticus tells the kids that anyone who treats a black man poorly, specifically by using his ignorance/illiteracy to cheat the man, is actually "trash". To Atticus, "trash" has nothing to do with social station, and everything to do with how a person conducts him or herself.