Christianity is not about virtues, even the virtues that have defined the Western World. Even if they epitomize God's law written on our hearts. Something is Christian if it points to the bodily death and resurrection of Jesus Christ, the only begotten Son of God. There are many Christian churches that will tell you that these virtues in and of themselves are what Christianity is about, and therefore Harry Potter is Christian. J.K. Rowling will tell you this, herself.
That's why I found this post on Get Religion by tmatt to be very interesting, especially this quote:
For several years now, I have been arguing that Rowling is, in fact, what her writings suggest that she is. She is a very articulate, liberal mainline Protestant storyteller (Church of Scotland, in this case) whose academic background has baptized her in ancient Christian language and symbolism. It’s hard to read the coverage of the final book in the series — heck, it’s hard to read the final book itself — without seeing evidence of both sides of this equation.