What quote from To Kill A Mockingbird supports the sentiment expressed here: "Judging a person does not define who they are, it defines who you are"?
In Chapter 3, Jem invites Walter Cunningham Jr. over to their house for dinner. While Water is eating, he begins to pour syrup all over his meat and vegetables. Scout is appalled and asks "what the sam hill is he doing." (Lee 32) Walter is embarrassed, and he quickly puts the saucer down and bows his head. Atticus looks at Scout and shakes his head. Scout begins to protest again and tries to explain that he's "drowned" his dinner in syrup. Calpurnia tells Scout to follow her into the kitchen and proceeds to yell at Scout for her rude comments. Cal explains to Scout that Walter is their company, and she needs to treat him with respect, regardless of how he chooses to eat. Scout argues that Walter is not their guest because "he's just a Cunningham." Calpurnia says,
"Hush your mouth! Don't matter who they are, anybody sets foot in this house' yo' comp'ny, and don't you let me catch you remarkin' on their ways like you was so high and mighty! Yo' folks might be better'n the Cunninghams but it don't count for nothin' the way you're disgracin' 'em---if you can't act fit to eat at the table you can just set here and eat in the kitchen!" (Lee 33)
Calpurnia teaches Scout that her manners are a reflection of her character after Scout judges Walter Cunningham Jr. for his eating habits. When Cal says, "it don't count for nothin' the way you're disgracin' 'em," she means that Scout's family reputation is useless when she disgraces other people by judging them. Scout learns that judging Walter says more about her rude manners than it does about Walter's eating habits.