In Chapter 9 of To Kill a Mockingbird, Scout fights with Francis, Aunt Alexandra's grandson, when Francis says that her father, Atticus, is a "nigger-lover." He is referring to Atticus's defense of Tom Robinson--a brave act that was almost unheard of for a white lawyer in the South at that time. Scout defends her father, and she and Francis get into a fight.
Jack, who is Atticus's brother and Scout's uncle, lectures Scout about getting into a fight, though he later repents and wants to punish Francis for what Francis said. He also lectures Scout about using bad words, and when she asks the meaning of the term "whore-lady," he tells her a long story that does not really make sense to her.
When Atticus hears what Jack said to Scout, he tells him, “Jack! When a child asks you something, answer him, for goodness’ sake. But don’t make a production of it. Children are children, but they can spot an evasion quicker than adults, and evasion simply muddles ‘em." In other words, Atticus tells Jack to give children straight answers to their questions, as they can sense a lie and telling lies only confuses them. Atticus thinks that children should be answered honestly and directly so that they come to understand the world. He also believes that all children use bad words and that only by ignoring them does their use of bad language end.
These two elements--Scout's fight with Francis and Atticus's advice to Jack to tell children the truth--connect to the value of having Scout as a narrator. As when she fights with Francis, Scout wants to defend what is right, and she will continue to do so throughout the novel. In addition, she will continue to ask Atticus what is going on around her, and he will answer her in honest ways. That way, she can use her role as a narrator to ask hard questions about the unfairness she sees around her, such as during Tom Robinson's trial, and Atticus helps her understand it.