The reason they had it wrong is because they didn't understand that to follow Him meant a full committment, a full taking in of who He was and what He said.
To completely follow what Jesus said is likened to eating His flesh, likened to eating His blood.
Another reference to explain this is to refer to the Passover Lamb.
What were the Jews to do with the Passover Lamb?
Here is something from an essay I wrote once:
In the Book of Exodus, we read of the Passover, the first Holiday commanded by God as given to the Jewish people.
12:1 And the LORD spake unto Moses and Aaron in the land of Egypt, saying,
2 This month shall be unto you the beginning of months: it shall be the first month of the year to you.
Note here, that God declared this Holiday so profound, that the month that it was in, was to mark the beginning of a new year for the Jewish people. The month to celebrate the Passover was to now be the first month. The Jewish people in the start of their year were being told to remember God in a wonderful way.
3 Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house:
4 And if the household be too little for the lamb, let him and his neighbour next unto his house take it according to the number of the souls; every man according to his eating shall make your count for the lamb.
5 Your lamb shall be without blemish, a male of the first year: ye shall take it out from the sheep, or from the goats:
This is a significant point. The LAMB of the Passover must have been selected previously in order that the Jewish people knew they had a perfect lamb for this feast day, but it was this day, the 10th, that it was to be declared to be THE LAMB, the one they would sacrifice and eat.
6 And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.
For 4 days, this LAMB was known to be THE LAMB until it was killed and eaten for the Passover. The Jewish day began at Sundown, so it was the 3rd day after the Day of Presentation that this LAMB was to be killed, to be eaten at the beginning of the Passover Day, which began at 6PM. This means that in order to have the LAMB killed and prepared for the meal at 6PM, the LAMB had to be killed beforehand. Jewish tradition is that the LAMB was killed around 3PM on the 13th of the month, dressed, and prepared for the Passover meal immediately after 6PM, the beginning of the Passover on the 14th.
7 And they shall take of the blood, and strike it on the two side posts and on the upper door post of the houses, wherein they shall eat it.
8 And they shall eat the flesh in that night, roast with fire, and unleavened bread; and with bitter herbs they shall eat it.
9 Eat not of it raw, nor sodden at all with water, but roast with fire; his head with his legs, and with the purtenance thereof.
10 And ye shall let nothing of it remain until the morning; and that which remaineth of it until the morning ye shall burn with fire.
Note here that the entire animal was to be eaten. Nothing was to remain. It had to be a total acceptance of the LAMB as a meal. The Jewish people were not to eat just the legs, or just the ribs, but the entire animal. This was the lesson taught to the Jewish people. God said to eat it all, and let none remain, and if your family was too small to at it all, have friends over to help you finish it.
11 And thus shall ye eat it; with your loins girded, your shoes on your feet, and your staff in your hand; and ye shall eat it in haste: it is the LORD’S Passover.
12 For I will pass through the land of Egypt this night, and will smite all the firstborn in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgment: I am the LORD.
13 And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and the plague shall not be upon you to destroy you, when I smite the land of Egypt.
14 And this day shall be unto you for a memorial; and ye shall keep it a feast to the LORD throughout your generations; ye shall keep it a feast by an ordinance for ever.
Note here that after the Passover, there was to be deliverance. The people were to be ready, to move, to act on what God said, fully clothed, and with your shoes on. God was coming to enact judgment! What is also interesting, is that those who were obedient to God, would not have this judgment upon them, they would be PASSED OVER. God’s judgment would not affect them if they put the blood over their doorway in the manner God said. It was to be over the top and along the sides.
To eat the Passover Lamb was to eat all of what God Commanded them to eat, right?
To NOT eat all of it was to disobey God, right?
What was Jesus called?
John 1: 29 The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world.
Note that Jesus is called the LAMB OF GOD. We have seen earlier, that it was a LAMB that was to be chosen to be sacrificed for the feast known as PASSOVER. John called Jesus THE LAMB OF GOD. If the Passover LAMB was to be a type of Christ, then there should be a connection between the death of the Lamb in the Passover feast and Jesus Christ’s death on the Cross.
I believe the purpose of Christ’s death was foreshadowed in the death of the Passover Lamb:
Exodus 12:23 For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you.
24 And ye shall observe this thing for an ordinance to thee and to thy sons for ever.
25 And it shall come to pass, when ye be come to the land which the LORD will give you, according as he hath promised, that ye shall keep this service.
26 And it shall come to pass, when your children shall say unto you, What mean ye by this service?
27 That ye shall say, It is the sacrifice of the LORD'S passover, who passed over the houses of the children of Israel in Egypt, when he smote the Egyptians, and delivered our houses. And the people bowed the head and worshipped.
Christians understand the meaning of this as the Egyptians are the representing of Sin in the Believers life before they are Born Again. When a person is Born Again, they pass under the Blood, they are saved by the Blood of Jesus Christ, shed on the cross for our sins, that we are no longer servants of sin, but alive unto God. By being UNDER THE BLOOD of Jesus, we are no longer going to suffer the penalty of eternal separation from God at the time of our death, symbolically, the Angel of Death will PASS OVER us.
(Rom 6:17 KJV) But God be thanked, that ye were the servants of sin, but ye have obeyed from the heart that form of doctrine which was delivered you.
(1 Pet 1:18 KJV) 18 Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers;
19 But with the precious blood of Christ, as of a lamb without blemish and without spot:
Being a slave in Egypt is likened to being a slave to sin. When a person is Born Again, they are released from this bondage, being now a child of God. They are to approach this life with their clothes fully on, and their shoes on, just like the Jews were told to eat the Passover meal, fully clothed, and with their shoes on their feet, ready to move, ready to live for God. While the Believer will still suffer temptation and still sin, Jesus Christ paid the penalty for their sin, and the bondage of eternal punishment is over.
In addition to this, Jesus once said:
(John 6:54 KJV) Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
(6:55 ) For my flesh is meat indeed, and my blood is drink indeed.
(6:56 ) He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him.
(6:57 ) As the living Father hath sent me, and I live by the Father: so he that eateth me, even he shall live by me.
(6:58 ) This is that bread which came down from heaven: not as your fathers did eat manna, and are dead: he that eateth of this bread shall live for ever.
For the connection to the Passover Lamb to be made through John the Baptist, we should see other references, and this passage from Jesus, telling believers they must “Eat His flesh and drink His blood”, can only refer to the Passover Lamb and the requirement that the Israelites eat the whole animal; yet to be a spiritual reference to eating: to consume who Jesus is, to consume the writings of Jesus, the teachings of Jesus, the life of Jesus; to be played out in the life of the Believer in obedience to God through Christ.
Here is the link to the entire article, it covers a different final subject, but goes into more detail on the conection of Jesus to being the PAssover Lamb.
For Jesus to be called THE LAMB OF GOD, and for the PAssover Lamb to be eaten in full, and since NO ONE is ever told to physically eat another human being or part of them, this reference HAS to be an allegory, and the Passover Lamb is that allegory.