John 6:63
"It is the Spirit who gives life; the flesh profits nothing; the words that I have spoken to you are spirit and are life.
YOUR mistake is that you actually believe that Jesus is talking about 
HIS flesh here - and that 
HIS flesh avails 
"nothing".
Jesus' flesh and blood avails us 
EVERYTHING, as it was the 
sacrifice of His flesh that 
paid for the 
SINS of the world.
To 
properly understand this verse - you need to look at 
ALL of the verses leading up to it. Jesus was telling an 
UNBELIEVING crown that they need to 
eat (trogo) His flesh and 
drink His blood in order to have Life. He went onto say that His flesh was 
TRUE FOOD and His blood was 
TRUE DRINK (John 6:55). He told the crowd: 
"No one can come to me unless the Father who sent me draw him, and I will raise him on the last day" (John 6:44).
By the time we get to 
verse 63 - the crown is just about ready to 
walk away from Him. 
THIS is where He tells them that they are thinking with 
fleshly human logic instead of 
spiritual logic from above. Christ was trying to
He 
wasn't telling the crowd that 
HIS FLESH didn't profit them.
He was telling them that their 
FLESHLY THINKING didn't profit them.
THIS is why He says right 
after this:
John 6:64-65
"But there are some of you who do not believe." For Jesus knew from the beginning who they were who did not believe, and who it was that would betray Him. And He was saying, "For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father."
This truth had not yet been revealed to them by the Father, so they could ONLY use their fleshly minds to discern it.
As we know - in the very 
next verse 
(John 6:66) - they 
abandoned Him and returned to their 
former way of life.
Did Jesus try to 
stop them to say, "Hey - I was just speaking 
metaphorically! Let me explain!"
NO. He turns to the 
Twelve and says: 
"Do you ALSO want to leave?" (John 6:67).
Peter speaks for 
ALL of them when he responds with. 
"Master, to whom shall we go. You have the words of eternal life" (John 6:68).
They 
didn't quite understand either - but they 
TRUSTED in Him.
MOST of His followers 
abandoned him that day for the 
SAME reasons 
YOU are arguing because they leaned on their 
OWN understanding instead of relying on 
God's (Prov. 3:5-6).