You are so correct.  I really have a hard time believing that so many parents that claim to be Christian, cannot understand that they are promoting the destruction of their own children.
 
Yes, I said destruction!
 
I personally know several families who have teens, and young adults who are by now so messed up,  trying to destroy themselves because they are demon possessed, and do not know  how to get back to normal.  Absolutely tearing the whole family apart.  No it is not drugs....however, most will  turn to drugs and/or suicide.  Some are put into institutions where the use of psychology,  which deals with the mind, emotions, and behavior, are used trying to heal them.
 
This is why God did not want his people to have anything to do with sorcery, witchcraft, magic, or any other ungodly agonistic practice. He knew where it would lead.  Playing with fire will get one burned.
 
Your question: Where have we gone wrong?
 
The answer: By not knowing the Word of God, or,  those who knew didn't have the backbone to make a stand, or did not really think it mattered.   "After all, it's just a fun childish fad."  Pastors and parents will have to answer to God for this gross sin. The blood of the this generation will be on their hands.
 
The part about Harry's blood is just a way of transferring this generation over to trusting in Harry's blood instead of the blood of Jesus Christ, who is the only way, the only door, the only salvation. We are commanded of God not to eat or drink any blood or be cut off (die in some way).
 
Gen. 9:4  But flesh with the life thereof, which is the blood thereof,  ye shall not eat.
 
Lev. 7:26-27  Moreover ye shall eat no manner of blood, whether it be of fowl or of beast, in any of your dwellings. Whatsoever soul it be that eateth any manner of blood, even that soul shall be cut off  from his people.
 
Lev. 19:26-31  Ye shall not eat any thing with the blood: neither shall ye use enchantment (casting spells), nor observe times (astrology).  v 28. Ye shall not make any cuttings in your flesh for the dead, nor print any marks upon you (tattoo): I am the Lord.  30. Ye shall keep my sabbaths, and reverence my sanctuary: I am the Lord.
31. Regard not them that have familiar sprits (sorcerers),  neither seek after wizards (witches), to be defiled by them:  I am the Lord your God.
 
Acts15:29 That ye abstain from meats offered to idols (false gods in pagan rituals), and from blood, and from things strangled, and from fornication: from which if ye keep yourselves, ye shall do well.
 
There are many scriptures pertaining to this subject.  Just a little research will show us that our families, our people,  our church, and our nation is in a whole lot of trouble. We need to repent, fast, and pray.
 
Webster