Comment by gwern

It's not supposed to be funny. The shock twist of it being cannibalism is supposed to make you think about the nature of default cultural assumptions and meta-ethics: "what factors Tardo would consider significant—probably very minor ones that the average man would not notice, he thought", and which the host fails to think of despite attempting to hide the slavery & cannibalism, in the same way that you might serve a visitor from India cow steak. (The author was from Brazil, incidentally, which may be relevant to how you interpret this: https://sf-encyclopedia.com/entry/fontenay_charles_l )