Reading the site further I found this to explain why they say there is demon possession in HP.
[From n1390] "Most occultists deeply desire to spend more and more time in their Fantasy World . They can travel there through Astral Travel, in which their soul actually leaves their body to go into the next dimension; of course, a demonic spirit must remain in the body to keep it from dying, as it will when it has no spirit. The Bible speaks to this fact most clearly; in Genesis 25:8, God describes Abraham's death in this manner: "Then Abraham's spirit was released , and he died ..." [Parallel Bible, KJV/Amplified Bible Commentary].
Occultists can also enhance their entry into the Fantasy World through drugs, especially the hallucinogenic variety. These drugs are so effective in transporting a person through the Fantasy World that they are highly sought after by occultists. However, these hallucinogenic drugs also debilitate the mind so much that the Illuminati forbids any of its members from taking them.
Occultists can also enter their Fantasy World through advanced visualization. Children are being taught Visualization techniques through Public Schools, sometimes as far down as First Grade under the guise of relaxation techniques during recess. Now, you know the ultimate end such satanic practices can bring a person."
The explanations for the rest are also reliant upon the authors supposed "knowledge" of witchcraft (and the Illuminati), and are also completely insane.
Btw, they have articles on all seven books, and I doubt that they're new, though they are definitely fundie.