It's painfully obvious that MC is someone who never picked up a history book, looked at a history documentary, or God forbid, watched the History Channel (or it's Japanese or Iraq equivalent) or watched some history vids on YouTube. Much of what the older man believes is something you'd have seen in almost any ancient culture minus the cannibalism, but the even that in a way is not anything new. Some ancient cultures believed they got strength from what they ate, etc.
This story is interesting, but the one critique I have is that the author is keeping MC stuck in pre-apocalyptic way of thinking without any real compromise or assertiveness to prove his point. He throws a tantrum like a child and runs away from the conversation.