Atticus treats Walter Cunningham respectfully. He speaks to Walter like an adult, showing Scout that Walter is viewed differently by Atticus than by certain other people, like herself. Walter shows himself to be capable and competent in conversation, talking intelligently with Atticus about farming.
During this episode, Walter demonstrates he has a number of differences from Scout: He soaks his food in molasses and talks with adults as an adult; Scout, petulant and indignant, acts like a child and is treated like one. Calpurnia scolds Scout for being rude to her "company," while Atticus goes on cordially talking with Walter.
Scout learns here to be more respectful and also begins to realize that people have potential that she cannot always see.
Atticus gives respectful treatment to Walter Cunningham at lunch on Scout's first day of school. Some adults treat children as though undeserving of respect, for example, Mrs. Dubose, although Atticus and the adult Scout would remind us that Mrs. Dubose is to be forgiven because of her illness and it's tragic complications.
Atticus's respectful behavior comes from intelligence, and accepting tolerance; he is the product of "gentle breeding," as Aunt Alexandra would say. Atticus is a perfect gentleman and host to anyone in his home—be it man, woman or child.
This scene is one of the first where Atticus shows his humility and acceptance of others, no matter who they are. Throughout the story, the reader sees Atticus socially and professionally engage with all sorts of people from all different classes in Maycomb County, and he is never prejudiced or disrespectful. In a community full of hypocrites and racists, Atticus is not one of them. A good description of Atticus's true character would come from what Miss Maudie says about Atticus's demeanor in the courtroom; he's a man of integrity, respect and honor:
"He's the same in the courtroom as he is on the public streets" (199).