Not A Book About Diversity...
...it's a book about hate.
Why? Because the author is clearly stating that if you are not mixed race than you are mean to anyone who is. That if you are mixed race you are smarter, stronger, and better than a race that isn't mixed.
If you want to spread goodwill and a positive message, then it should be acceptance of all races as they are, to teach kindness and demonstrate how all people are the same on the inside, though they may look different on the outside and that each person may have special skills that sets them apart or they may just have skills similar or on par with other people, but that doesn't make them less.