Zack Beauchamp feels that it's the reversion to "tribalism that makes The Walking Dead‘s apocalypse so chillingly real":
Modern moral progress, as Peter Singer argues, has proceeded by expanding the sphere of moral concern to an ever-larger group of people. People may have once only cared about those who share their nationality, race, or gender, but as Enlightenment ideals about universal human rights took root, humans have moved inexorably towards treating everyone as equally worthy of moral concern. The Walking Dead‘s third season has suggested that, when you demolish a stable society, this purported moral progress will have proved a smokescreen, and that our enlightened selves are just as brutally tribal as our ancestors.
The moral drama in the struggle between the two groups of survivors, then, isn’t over the appropriateness of groupism in the shadow of the End. Instead, it’s about how we rebuild our moral code from the ashes.
Scott Meslow notes the emergence of a theme in the show's latest episode:
I'm not willing to call The Walking Dead some kind of pointed allegory for the war on terror, but there are some parallels being drawn here that shouldn't be ignored.
The Governor has earned the unwavering loyalty of the Woodbury residents by offering them the security and the semblance of the lives they used to have. They live in actual houses, have an ample supply of food and alcohol, and walk down zombie-free streets. In return, they agree to give up certain freedoms, and don't ask too many questions about how the Governor ensures their security. And notice how easily the Governor convinces his followers that the others–including their erstwhile protector Merle–are an enemy to be vilified and destroyed.
One of the biggest themes of The Walking Dead has been dehumanization, which we've seen in a few forms. There's the literal dehumanization when a person becoming a zombie. There's the survivors' need to accept that their loved ones are no longer human after they've turned–a process abetted by calling them "walkers" or "biters." And most subtly–but also most importantly–there's the othering of fellow human beings with labels like "terrorist," which can turn a group of people into a bloodthirsty mob within moments.
The Dish 