I get the analogy, but it's too extreme and therefore falls apart. I don't expect
people in these circumstances to hold onto their humanity. It's simply unrealistic.
People in far less extreme circumstances have lost their humanity and done terrible things, and then guess what, when you look at the situation in retrospect nothing bad happened as a result.
Here's an example: the extermination of Native Americans in order to create land for white people to settle and create America. That was bad, but the badness was never punished. In fact, it was rewarded with success and material gain. History is full of examples like that.
It's a replay of the problem I had with nuBSG
. When you're talking about the survival of a species, morality simply doesn't count. The smart thing to do is forget morality and make sure your species survives. Then you'll have some descendents, and they won't give a flip what you did in order to make sure they existed. If your species is exterminated, then there will be nobody left to praise your morally upstanding ways.
The idea that it's important for people to "hold onto their humanity" is a romanticized notion that doesn't actually hold up to an examination of the shit people do get up to, and whether they are rewarded or punished for it. The world is a very unromantic place. Evil has always gone unpunished, under far less understandable circumstances than a zombie apocalypse, and evil will continue to evade punishment long after all of us are gone. Power is far more important than morality.
But for the purposes of drama, I'll accept that it's important for the people in this story to hold onto their humanity, for personal reasons, and enjoy the story that unfolds as a result. As long as it's internally consistent and psychologically believable, it doesn't matter that it actually has no applicability to the real world. I don't condemn Shane's actions, for instance, but I fully expect them to have serious psychological repercussions on him, which will be interesting to watch.