The problem with that is that just like with antibiotics you're left with the ones which they don't kill, you'll be left with those who would actually rather enjoy watching people getting killed.
I mean, what's the solution to these types of problem where the adversary keeps getting better and better? I feel like Forever War touched on this too, where the Taurans just kept getting more and more advanced, and it was always an arm race to have the better technology and better weapons and better tactics, etc.