I can't explain everything in the Harry Potter series,
There are actually reviews of the series that have been published that discuss the various elements of the story. They're unbiased, though, so you will want to avoid them.
I just know that it is evil.
It's fiction. Your cult is the only group that believes it to be "evil."
I know because I use to dabble in the paranormal before I was converted .
Translation, I used to read my horoscope every day.
Its designed to seduce children,
No, it's designed to entertain.
its pathway is to demonic influences,
No, it's pathway is to entertainment.
its designer is Satan
No, it's designer is a British author.
There's Nothing new under the sun , its just a repackaged seduction and indoctrination to the evil one for the 21st century.
Hardly. If anything, it argues for destruction of evil, triumph of good, all that stuff.
Why does it surprise anyone that a person like our President would be so fond of the story for his little girls?
I doubt it surprises anyone. It's popular fiction. His daughters have probably read it and enjoyed it. Being open-minded and rational, Obama allows them to read it.
He is no Christian
That's debatable. He may not be fundie, but he identifies as a Christian. According to everyone other than your cult, that makes him a Christian.
but Michele's Mother is said to be one. So let us pray she has some influence there in that White House.
Well, that's somewhat better than hoping an invisible man has influence over the White House. At least Michelle's mother is real.