The final statement of Atticus Finch about people returns to his early remark to Scout to not judge people without getting to know them (Ch.3):
"You never really understand a person until you consider things from his point of view--
--until you climb into his skin and walk around in it."
For, little Scout tells her father about a character in The Grey Ghost, but metaphorically, the character to which she refers is Boo Radley as she describes him, "Atticus, he was real nice."
Atticus replies, "Most people are, Scout, when you finally see them." Atticus recognizes that Scout has certainly matured now that she demonstrates that she understands what it is to "walk around" in someone's skin.