The Bible specifically addresses slavery as a good thing. If God says it's okay, then it must be moral, huh?
Your example is, of course, an extreme one and not likely to affect society as a whole. A similar situation to what you describe actually happened to the crew of a whaling ship in the mid 19th century. The upshot was that, before they were rescued, a couple of them had been killed and eaten by the rest. No one was prosecuted for the killings (the victim's were chosen by lot) or the cannibalism, as the pragmatic and very Christian folk from these whalers' homeport felt the men did what they had to do under the circumstances.
Do those circumstances hold true for society as a whole? Nope.
There is such a thing as absolute right and wrong. And it is not defined by Mullah, or Nazis, or Christians, or agnostics, or atheists, or votes of groups, or evolving standards, or societies. Or rational self interest.
For animals, there are only actions and consequences, I don't believe people are only animals, even allegedly smart animals. Liberals mostly do. Some others do as well.
We will never agree. Peace
The Bible addresses slavery as an existing thing not as a good thing.