According to Christian beliefs, witchcraft and sorcery are evil things. Some Christians pointed out that Harry Potter is dangerous because it teaches witchcraft to people.
Some scholars argued that getting direct exposure to occult over and over can make people become comfortable and familiar with it.
Getting used to devious spirits
Some Christians suggested that watching Harry Potter can make people get used to devious spirits and so force them to move away from the way of God.
Marketing a new belief system
Some Christians suggested that Harry Potter markets a new belief system as its main product and that this belief system goes against christian teachings.
Supporting Pagan practices
Some Christians argued that Harry Potter books and movies support Pagan practices and make people more familiar with them. (See Why is Harry Potter so popular?)
Some people pointed out that the real danger of Harry Potter is that it targets many children who don’t have enough knowledge about the Bible or witchcraft, and as a result, can be brainwashed easily.
Comments from churches
Many churches have made comments that state that Harry Potter is evil and demonic. This led to a controversy that made the matter more popular. (See Why controversy can make things popular?)
Indirect way to change beliefs
Many Christians argued that Harry Potter targets the subconscious mind and that it is a sneaky way to change people’s beliefs about God and magic.