His hearers are grossed out, recognizing the cannibalistic metaphor. If we discussed the Gospel reading like we do the others, it wouldn't take long before somebody in this congregation expressed distaste for the central metaphor. We'd agree with those who took objection to it as they heard it. It's always a surprise to see that Jesus does not heed the canons of respectability in his speech. We've been raised with him as the example of goodness and with decent talk as a marker of goodness, so it takes some getting used to that his impatience doesn't wait to accommodate our expectation.
Some people never let themselves see the problem.
Lets us get past that. The list goes on and on. So we ought not to be so surprised when he offers his own body to us as though we were each repressed cannibals craving relief. We can only speculate as to why he carried on like that. When I behave like that, I'm being immature, the self-display of an unresolved adult adolescent.