What important lesson does Jem learn from his experience with Mrs. Dubose in To Kill a Mockingbird?

In Chapter 11, Jem is forced to read to Mrs. Dubose as a
punishment for destroying her camellia bush. Mrs. Dubose is an ignorant racist who hurls
insults at Jem and Scout as they pass her house. She tells Jem that Atticus is no better
than the "niggers and trash" he works for and insults Scout for wearing overalls. While
Jem reads to her, she continually corrects him and makes negative comments. Later on in
the chapter, Atticus gives Jem a gift from Mrs. Dubose, who recently passed away. Inside
a cardboard candy box is one white camellia in perfect condition. At first, Jem freaks
out and says, "Why can't she leave me alone?" (Lee 148) Atticus
tells him to settle down and explains that it was Mrs. Dubose's way of telling Jem that
everything is alright. Atticus then tells Jem that she was a great lady who had
tremendous courage for battling her morphine addiction. Jem is surprised to hear Atticus
speak so highly of the old, cantankerous Mrs. Dubose. Throughout this
entire experience, Jem learns an important lesson in the duality of human
nature. He learns that even the unfriendly, ignorant Mrs. Dubose has
positive characteristics. Jem's childhood innocence led him to generalize all people as
either good or bad. In Chapter 11, Jem learns that individuals can have
both good and bad qualities. This is one of the many eye-opening
experiences that impact Jem's understanding, growth, and moral development.