If you kill you get killed.
An eye for an eye....
Load of old cobblers, and entirely nonsensical if you actually think it through beyond the simplistic idea because it applies equally well to both sides. So now you're into the justifications and rationalisations.
Both sides kill, and
both sides retaliate based on the idea quoted above. Ah, you say, but they killed first. Ah, they say, but our people died because of your actions in some time and some place, so actually
you killed first. Ah but, you say, we only took those actions because something you did led to some deaths even further back, so actually
you killed first. BUT, they say... and so on
ad infitum. And going forward, we kill in retaliation, then whoever's left retaliates against us, so we retaliate again, and so on
ad infinitum.
The point is that for either side the idea that the enemy must be 'wiped off the face of the earth', as you put it, is just about the most stupid response possible.
But what do I know, I'm just a weak lefty liberal, after all...