Every era gets the fantasy it needs. The early twentieth century had Peter Pan- rich pickings for Freudians and all that weirdly prescient stuff about lost boys. The second half of the 20th century had Tolkien- with his ethos of cold war paranoia and unwitting prophecy of flower power. And Harry Potter is the fantasy for the Noughties.
Fantasy gets to places the realist novel can't reach. At its best it doesn't try to teach us anything (which is why C.S. Lewis and Philip Pullman are lesser writers) it just tips the contents of what Jung called the collective unconscious at our feet. In hindsight it looks as if Rowling were writing a fantasy commentary on the Blair years- the scurvy politicians, the war on terror, the cynical trampling on civil liberties- but, of course, the whole series was planned in detail in advance. Azkaban isn't a reflection on Abu Ghraib and Guantanamo, but a prophecy.
And he notes that those who have dismissed the Harry Potter stories as simply escapist are pretty far off the mark. The fantasy world of the Harry Potter stories has some remarkable resemblances to the real world. And his response to reading The prisoner of Azkaban comes even closer to the mark
Then there's that other prison: the Guantanamo Bay-like hell-hole of Azkaban. In the first two books evil has been concentrated in the person of Voldemort (the enemy, the other, the dark lord, out there) here Voldemort never appears except in discourse and the focus of evil is Azkaban and its disgusting Dementors who- disturbingly- are on our side.
So, if we employ Dementors and send people who break our rules- like the innocent Hagrid- to a place where it's guaranteed they'll lose their minds if not their very souls- how exactly are we better than Voldemort?
One point on which I disagree with Tony Grist is that I believe Rowling, like C.S. Lewis and Philip Pullman, does try to teach us things. Her blending of different genres (the school story and the fantasy story, for a start) enables her to go beyond the simplistic moral universe of classic school stories like the Billy Bunter series, for example. As Tony Grist himself notes, she teaches us that moral choices are not always simple. Like other school stories, the Harry Potter stories show some perennial problems in the school environment, like bullying; but Rowling also show how the pattern of moral behaviour formed at school continues in later life.