Does Harry Potter promote occultism?
Depends on what you mean by promote. The book has wizards, witches, potions, magic and other supernatural references. Does it encourage people to become wizards, witches, etc? No. But it makes these fictional characters who use magic and supernatural forces seem normal and ordinary. To fundamentalists and extremists, this is promotion of the occult. To more liberal minded people, it's just a good fairy tale.
I have enjoyed the movies and the books. I don't see it as harmful when you take it for what it is, a fairy tale fantasy. The one thing that did stick out as unusual to me though was the fact they observed Christmas and Easter holidays. So these are Christian wizards? I don't see the connection. Halloween makes sense but not the Christ related holidays. Just shows that it's a story meant to be enjoyed and not dissected I guess.