Your question poses an extreme scenario which does not fit the debate - your hypothetical involves a non-Christian, by definition. But what you are telling all is that a detail of interpretation defines whether or not one is in the faith. Before I would take such a rigid position, I would make damn sure I had done everything possible to determine the accuracy of that interpretation - not just take Rome's word for it. What does the passage upon which you rely say in Greek? Hebrew?
Again - the cannibalism question isn't what is absurd. The response demonstrates that. You have just told us all that it is okay to eat flesh as long as it is disguised as bread. Is that really what you believe the Bible teaches us?
Reread John 6.