The adult narrator, a grown up Scout Finch, reveals a great deal about the citizens of her home town through her childhood memories. Children do not excuse or ignore events or traits that are indicative of a person's personality. In addition, the way people treat children is often an excellent indicator of their character; a person who is kind to children is probably a kind person in general, while a person who takes advantage of, or is cruel to, children will probably treat anyone with less kindness than he deserves.
Children really see people as they are, for the most part. When the believe something to be true of someone, such as in the case of Boo Radley, it is because they have been taught to believe it. For the most part, children are able to perceive the truth of people's natures, although they may be overly dramatic in doing so. For example, Scout sometimes thought that Calpurnia was a tyrant, but also knew that Calpurnia loved her dearly.