I am a strong evangelical Christian. I love the HP books. I can see a strong surprising current of Christian oriented morality in them (importance of family and friends, importance of making good choices, how love protects us).
But the setting of magic and witchcraft is upsetting to many Christians. They think the books are evil.
Most of us who read them don't advertise it, some of us for no other reason than out of love, because others of us have had very bad experiences with the occult. So I could see how some Christians could recommend them and others could hate them.
Besides, lets face it. A man who has never had any kids is probably the kind that will tell you never let your kids watch TV anyway, and they should only read classics and uplifting books, and never have meals consisting of french fries. My friends without kids always told me that, too. :)
An English teacher of mine said that if evil is portrayed as evil, it's good. I've seen two of the HP movies, and it was a story about good vs. evil, and the evil was clearly defined. To me, it's no different than the Star Wars saga. Evil is shown as evil, and whether that evil is destroyed by magic or the force, it's destroyed. Magic can be symbolic of our own power to overcome evil. And of course, fantasy is just fun to escape into to get away from this uptight world.