Sometimes, one needs to become a monster to defeat one.
You can’t send an innocent person to defeat a demon. The demon will destroy the innocent man every time.
The story of Dexter is a “fictional” example of this.
Even Sun Tsu confronted this quandary in the Art of War. “If you are not capable of getting into the dirty ditch with your enemy, your enemy has already won.” (That’s a bad paraphrase, but technically accurate.)
The razor’s edge is this: Are you destroying a demon? Or are you hurting an innocent?
Tom Horn anyone?