The danger is not in seeing films like Harry Potter, but in not teaching kids what scripture says about magic, spiritism, astrology, mediums, etc.
If they know what scripture says, then they will know where to draw the line. If they don’t know what scripture says, then Harry Potter is but one influence in a world of influences that they will be unprepared for.
The world is full of “Christian Astrologers”, “Christian Mediums”, people who claim to talk to angels, various self-appointed prophets, religions started by self-appointed prophets, etc. You need to know what the Bible says about such subjects, or Harry Potter is probably the least of your concerns.
If one is an astrologer or medium, then one is NOT a Christian. Maybe a Christian in name only, but, not a true follower of the living Christ. Neither should a true Christian support any candidates who support the killing of unborn babies. I feel sad for those in the black community who are believers, but, also believe in and defend the zero in office. They are basing their support on skin color and not character. How sad, that they can be deceived this easily.