I might be completely wrong, not being a sci-fi fan or interested in either Lord of the Rings or Harry Potter, but I was told that the problem with Harry Potter was not about the spell casting, but the fact that power both good and evil came from the same source. I have no idea about the Lord of the Rings, not having read the book or seen the movies. Maybe someone with more knowledge of either could verify or deny that claim. I'm a "when in doubt don't" kind of gal, but those movies have not been an issue for me since I am not at all interested in them.
My husband watched Harry Potter and wanted to let my daughter watch it. I objected only for the fact that it wasn't something she needed to do and the only reason she would have been interested in the first place is because of all the media hype. She might have watched half of it and gotten completely bored and wanted to do something else. I was also a little concerned with the violence. I thought it might scare her.