Reading my book so far, I don't exactly see the problem with this book. It's basically a story about a boy who has been treated unfairly and gets beat up by it by his cousin Dudley. He gets "saved" by a grounds keeper at a school named Hagrid. Then you add a bit of magic here and there. I haven't gotten too far into it yet for me to see if anything has changed my mind but nothing yet.
I found some information on Infoplease about what a teacher from St. Mary's Island Church of England school in Chatham, Kent. This teacher says the following, "The Bible is very clear and consistent in its teachings that wizards, devils and demons exist and are very real, powerful and dangerous and God's people are told to have nothing to do with them. I believe it is confusing to children when something wicked is being made look fun."
This teacher isn't alone. There are other people in the world that think real witchcraft still exists, and that all witches are evil. People fear that any books have good magic or witches that it could lead people to to take this threat of witchcraft seriously and take the Bible's teaching lightly. They think it could lead the readers to become witches themselves.
Then you have the people that disagree with that. They say Harry Potter is a fantasy, not a true story, and claim that children would be able to know the difference between the two. Who knows if evil magic is even real or not, it doesn't have anything to do with all the made-up potions and spells found in the author's books. In the article, they use a editorial from Christian Century and they put it, "...critics are right in thinking that fantasy writing is powerful and needs to be taken seriously. But we strongly doubt that it fosters an attachment to evil powers. Harry's world, in any case, is a moral one."
Some argue, besides magic, that the book can set a bad example. When Harry and his friends break rules, lie and sometimes disobey the authority figures, including the professors at Hogwarts. Then he is being awarded and praised for it. Others say that during all of this, it's part of a long tradition in storytelling. To get the story outside of the ordinary, you need a bit of rule-bending. To point out, Harry's rule breaking does not go without any punishment. Finally, some believe that even heroes aren't perfect and on a whole Harry and his friends are positive role models.
People also point out the scary stuff. They say they're too dark and scary for children to read. When good people die suddenly and it's not for kids as entertainment. The other side of things, it's given credit. It's possibly a way to help kids learn how to deal with the reality of death. Diverse classics as The Red Badge of Courage, Charlotte's Web and The Hobbit. All of those novels include deaths of major characters, so Harry Potter fits right in.
I could go on and on about this topic, giving examples of why people think it should be banned and when others say it shouldn't. It's all about opinion really, so it's a matter of research and really what you think about Harry Potter if your religious or not.