How does the phrase "don't be fooled by appearances" relate to the novel?

Early in the novel, Marineau establishes the theme of narrow-mindedness by introducing characters who have difficulty seeing beyond their own perspectives and prejudices. Karim's unnamed classmate who also serves as narrator for part of the book looks upon Karim as a novelty within the classroom: she thinks he, as an Arab, would look more appropriate in a desert setting, riding a camel. Ironically, Karim soon reveals his own narrow-mindedness, admitting in his diary that he doesn't know if My-Lan is Vietnamese or Cambodian or Chinese, then referring to her as "that China girl." Beyond the racism in Karim's words is Karim's inability to see outside of his narrow, traumatized perspective. However, by the end of the novel, his perspective has grown. My-Lan becomes a friend and source of comfort; getting to know her more closely, he realizes that her experience as a Vietnamese immigrant means that his suffering is not unique.