"Becoming as evil as the enemy in order to defeat him proves what?"
YOU WIN. That's the ONLY way to win, to fight fire with fire.
And your premise is WRONG. Fighting evil with everything we got does not make us evil, it makes us effective.
Did our Navy respond to, and defeat the Nipponese kamikazes by having Navy pilots carry out suicide attacks?Did the U.S. and its allies carry out mass exterminations in camps set up for that purpose?And did you realize the firebombing of Dresden angered the German populace while destroying very little of military value?
Why copy the standards and techniques of losers?