For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
You can replace the words "harry potter" with christmas, easter, halloween, etc. Anything that comes from the secular pagan rooted idolatrous world should not be Christianized. It is confusing not only to children but to new Christians who have experienced these things before becoming Christians. God says to be in the world and not of the world. I wish Christians would stop blurring the lines and stand firmly in the Kingdom of God.
Personally, I think that the Harry Potter series is not of God and should not be viewed by children or adults. As Angel K said, the secular world has created it; it is confusing and God is not a God of confusion. To protect our relationship with our precious Lord, I feel that anything that presents doubt in our hearts or minds should be paid close attention to and rejected. I too believe that christmas, easter, halloween, etc. is of the secular world and Harry Potter is just another ruse of the world to confuse adults and our children. AS for me, I am so cautious on what I allow to enter into my children/grandchildren;s hearts and minds and Harry Potter is a "dressed up" evil. Please let us all be careful and discerning when it comes to feeding our children's minds. Pray for discernment and God will give it to us in all things that we struggle with.