What does John 6:52 mean?
Earlier, the crowd speaking to Jesus seemed willing to use force to make Him king (John 6:15). They demanded yet another miracle when Jesus began to correct their traditional views (John 6:30). They complained when Jesus claimed to be the "Bread of Life" sent by God (John 6:41). Now, Jesus has specifically said that the "Bread of Life" which brings salvation to those who believe is His own flesh (John 6:51). While this is symbolic of His impending crucifixion, the people react with even more aggression. Their conduct is described with the Greek word emachonto, which can include anything from vigorous debate all the way to brawling.The primary problem is that the crowd interprets a spiritual idea with a physical bias. Their first thought, then, is that Jesus is somehow suggesting cannibalism. For Jesus to suggest that belief, not good works, is required for salvation is scandalous enough (John 6:29). To invoke something as bizarre as eating His flesh is outrageous (Genesis 9:3–4; Leviticus 17:10–16).
In the next verses, Jesus will continue to expand on this metaphor, but most of the people will not accept it. Even for those who assume Jesus is speaking in metaphor, the idea that the Messiah is not a conquering king, but a sacrifice, is extremely hard to accept (John 6:60).