After everyone else leaves, Duke seems a little sour at the prospect that Mike would actually eat another human being. Go figure.
Jubal explains that Mike is granting him the greatest honor possible for Martian society, but Duke believes that the prospect is savage and that Mike is uncivilized.
Duke offers to eat in the kitchen and away from Mike. Jubal takes this to mean that Duke has resigned. He tells him to leave, but not before he tries to explain to Duke the flaws in his reasoning.
Jubal compares Mike to a coral snake. According to Jubal, the snake itself is not dangerous; instead, it's all in how you handle the snake. If you don't know what you're doing, then and only then does the snake become dangerous. Either way, it's not the snake's fault.
At this point, Duke and Jubal watch the tapes and discover that the box thrown at Jubal's head doesn't just wink out of existence but actually shrinks out of existence.
When viewing the incident from two separate angles, they see the box shrink out of existence in the same direction, which should be impossible. Duke thinks this means the cameras are faulty, but Jubal isn't so sure.
The two men return to the discussion of Mike and whether or not Duke is fired. Ready? Go.
Duke argues that he's always known that cannibalism is a sin. No one had to tell him—it's just natural.
Jubal totally disagrees. He says it's all because of cultural conditioning, lessons learned on a "mother's knee" so to speak (13.81). The icing on Jubal's argument cake is that every human culture has ritual cannibalism if you look far enough back in history.
The argument continues. Jubal definitely doesn't think that Mike is a savage. He's highly civilized, just Martian civilized. The cannibalism in question is never done to hurt another Martian or against a Martian's will. Instead, the ritual is deeply formalized, and the Martian being eaten dies only when he wants to.
Not convinced yet? Well, in once last effort, Jubal notes how Duke's religion has ritualized cannibalism in it as well. Well, then.
Religious Snack: Although Heinlein is being ambiguous here, he may be referring to the communion of Christianity. In some branches of Christianity, when the Blessed Sacrament (the wafer and wine) are consumed, they are believed to miraculously—and literally—turn into the body and blood of Jesus Christ. The process is called transubstantiation. But remember that in other denominations of Christianity, the taking of the sacrament is purely symbolic.
Oh, and whether or not Duke is fired remains an open question.