A recent paper published in Journal of Applied Social Psychology found that reader identification with with the main character of Harry Potter (and disidentification with Voldemort) positively correlated with reduced bias toward stigmatized minorities in real life. Researchers found this Harry Potter effect was significant even after controlling for the general amount of books read, which by itself is strongly associated with reduced bigotry and prejudice. So, it seems unfair to say the books are nothing but toxic.
What I want to know is the correlation between reading Harry Potter and how people think their ENEMIES should be treated. And what criteria determine what makes someone "bad" and how badly they deserve to be punished.
http://www.psmag.com/navigation/books-and-culture/harry-potter-battle-bigotry-87002/ *Update
The linked article is correct in its general summation of the findings, but is sloppily written. I'm not entirely comfortable reproducing the entire paper, but if there are particular sections people would like to see I'll try to either excerpt or summarize them more accurately. The paper itself is hardly groundbreaking - it's been shown before that reading about foreign perspectives helps increase tolerance. This mostly showed that the same effect extended to fantasy fiction. The studies were also extremely narrow in focus (only looking at identification with Harry or Voldemort). Mostly I thought people would be relieved that SOME good came from such a widely selling series, despite its numerous flaws.