When is it morally right to kill a zombie? The obvious answer is "ANYTIME!"
So does this mean that killing zombies is a morally questionable thing? It’s a trope that often plays an important part in the narrative of zombie stories. Imagine you’re the protagonist, and you have the opportunity to kill one of the undead. But you hesitate, maybe because you recognise the zombie, or maybe because you think you see a trace of the person’s past persona in the approaching horror. That split second of indecision could be enough for you to lose the advantage, and get munched on. But you have to appreciate that hesitation. The monster in front of you was once a living, breathing person with hopes, fears and dreams.