Talking to kids about diversity and tolerance is not something that happened when we 40-somethings were young. I don't recall a parent or a teacher ever bringing up the subject of diversity, and it really wasn't until I was in college in the early 1990s that I remember the notion of diversity actually being shown as a positive thing.
Now, children are taught from an early age that our differences are what makes our society awesome, and that everyone is equal. Duh.
This study is cool, showing a link between letting kids discover these ideas through fiction, rather than through real-life-examples.