It seems so easy to accept the words of the Bread of Life Discourse from the 6th chapter of John that we heard from in today's mass. We have the benefit of living after the great signs of John's later chapters and the death, resurrection, and ascension. We live in the era after the Holy Spirit descended at Pentecost. We have two millenia of tradition upon which to draw. It is enough for us to know that He said it. We accept that He was the Son of God. The crowds from today's Gospel reading didn't enjoy those benefits.
If I had been in the crowd, it is quite likely that I would have been disturbed by what I was hearing. Knowing the family life of the man making the claim and remembering his childhood would make his words even harder to accept, even if he was able to do miraculous things. I probably would have been one of those murmuring against Him, much to my detriment.
Do we take the time often enough to thank God that we don't have to figure all this out for ourselves? Don't get me wrong. There's still plenty for us to discern. But we already have so many of the really important, foundational answers. It means that we can focus our attention on actually trying to live up to what He taught. And God knows that, for me at least, that's plenty hard enough.