* That some would include me.CoC is like zombies in that the theory has been killed many many times. That it suffers from logic, from bad conceptual stretching/residual categories, from being rather unlike how the world actually works (identity matters, but not via civilizations), that there is more conflict within than between civilizations, etc. See the MC piece for cites to all of the abundant literature that has made the theory seem like the walking dead.
But Zombies can be killed and killed easily. Any movie or tv show (Walking Dead, Z Nation) has people killing zombies with guns, knives, baseball bats, chain saws, and so on. Any individual zombie can be killed easily.
How about Highlander's Immortal? They can only be killed via decapitation. And immortals become more and more skilled in using swords, so they become harder and harder to kill. In the end, there can be only one. Which then means that decapitation becomes incredibly unlikely. The problem here, of course, is that the Highlander that won, Duncan MacLeod, was a good guy, fighting evil-doers. Clash of Civilizations? Just enables evil-doers by making bad social science popular. More problematic for the metaphor battle is that Immortals are rare and become rare still--they cannot re-produce. The Darwinian battle amongst them does not help propagate the species at all.
So, neither zombie nor Immortal.... but zombie virus? Ah, yes, there we have it. You can kill heaps of zombies, but can you get rid of the zombie virus? Thus far, only love seems to conquer the virus. Otherwise, in most zombie pop culture, fear, anxiety, panic (the clash both is fear and is strengthened by it) all serve to help the zombie virus spread. While the carriers may die easily, the virus lives on and on.
We social scientists have been doing the best we can to fight the virus, but all we have done is slay some of those carrying the disease. The disease is now worldwide, alas. So, we keep fighting and fighting, and hope that some day a cure, perhaps a vaccination via intro to IR classes, can reverse the tide and eventually lead to the marginalization of the disease that is Clash of Civilizations.