I hope you will pardon my late arrival...
I too am a Christian. The group of Christians with whom I practice my faith shy away from Fundamentalism while embracing the Fundamentals of my faith. Lewis and Tolkien are honored, while Rowling seems to be an issue for continued discussion.
1. The original question.
Fifteen years ago, when I was still far too impressionable, and lived in the south (for a couple years) where Christian Fundamentalism is strongest, I felt compelled to disassociate myself Tolkien, and all of Lewis's fantasy, because it contained sorcery. Soon after I had made this decision, I was in a local Christian bookstore, perusing the racks, and noticed a book about the bad influence of Tolkien, Lewis, and all the rest. I checked it out and saw that the book was commenting on Galadriel as a well disquised witch who performs magic. The book admitted that Tolkien was popular with many Christians, but that they were being snowed by this author. Well, I knew better, and this extreme denunciation of something I knew to be very good, sort of helped remove the blinders in general.
2. Fantasy and Religion.
lindil is critical of Harry Potter because of an avoidance of religion. I find this interesting in terms of a recent discussion called
The Emblems of Religion don't belong ... or do they? . In this thread, some of the same readers that are posting to this thread, asserted that religion has no place in any fantasy work, and they further asserted that there was no religion to be found in LotR. Meanwhile, others were posting various evidences of religion sprinkled throughout LotR. What I hope is not being done on the Downs, is that an absence of religion is being praised in LotR while being denigrated in Harry Potter. That would be a double standard.
That there is a Christmas in each Harry Potter book seems to have more to do with culture than religion, it seems to me.
There is one thing that is consistent throughout Harry Potter, though. There is a consistent moral compass. I don't know where the poster got it from who said that characters changed sides at a whim. I, like
Imladris, never saw that in Harry Potter. If there was changing of sides, it was consistent with the story.
3. Feigned reality, feigned magic.
Tolkien wrote about his Legendarium that it was feigned history, feigned reality. Nevertheless, there have been many readers who have refused to view it as feigned. Likewise, Rowling has said that the magic in Harry Potter is feigned magic; yet there are readers who have attempted to use the so-called magic as if it was not feigned. The point is, it's feigned. It's not the real thing.
Being a Christian who believes the fundamentals of my faith, I wish believers and non-believers alike would not get their knickers all in a twist over magic in a story. It's a story, by gum! It's feigned magic. Just as everything in any story is feigned reality (including Eru

).