In an effort to bring this topic back on track (Hey, welcome back BrianH!!),
The question was raised, “Why did the Jews leave… who knows?”.
Well, let’s look at the evidence.
Verse 41 says, ***The Jews murmured ***about him because he said, “I am the bread that came down from heaven,” Hmmm…, it looks like the Jews don’t like this saying.
The next time we look in on the Jews conversation, they are beginning to try and parse almost exactly what we are in verse 52 …The Jews quarreled among themselves, saying, "How can this man give us (his) flesh to eat?".
So, after Jesus once again repeats that you must eat His Flesh, the Jews are complaining again, in verse 60, Then many of his disciples who were listening said, "This saying is hard; who can accept it?"
Notice, these aren’t just the Jews that followed Jesus wanting more of that fresh bread. This group has been joined by some of Jesus’ followers. And they specifically are complaining about this command to Eat His Flesh. There’s no questioning the motive of their dis-belief at this point, IMO. It would seem they are having a hard time, shall we say “swallowing His Words”?.. Sorry, bad pun (can I have a rim-shot, Smitty?).
So, Jesus raises the ante even further, “Does this shock you? What if you were to see the Son of Man ascending to where he was before? It is the spirit that gives life, while the flesh is of no avail. The words I have spoken to you are spirit and life. But there are some of you who do not believe." … And he said, "For this reason I have told you that no one can come to me unless it is granted him by my Father.”
And this is the breaking point. For verse 66 tells us, As a result of this, many (of) his disciples returned to their former way of life and no longer accompanied him.
As a result of this, many disciples left him… As a result of what?
His talk on eating His Flesh, as I showed, could have caused the disciples to leave.
But his demand at the end, “no one can come to me…” could have caused them, for Jesus is implying that He is the Son of God.
So which is it? Well, this is not the first time Jesus has talked of being the Son of the Father and the like, which means if the disciples would have left Him, they would have left a lot earlier.
So, it seems logical to me, that they left over Jesus’ talk of eating His Flesh. Especially when you look at the Jewish Laws on blood and such (not to mention cannibalism).