During WW2 when the Nazis would murder US troops rather than take them prisoner from time to time, then for weeks allied troops would shoot Germans trying to surrender. Once it became clear that the Germans where playing by the rules again the Allied started taking prisoners again. If one side violates the rules the you have to retaliate. If we're lucky the left will return to playing by the rules but they certainly won't consider doing so without a taste of thier own medicine.
You can call that barbarity but my own reading of history indicates that civilized behavior is only to be extended to people who practice civilized behavior. Since WW2 the left always insists that we extended civilized behavior towards barbarians while the left endlessly uses barbaric proxies to attack us. We've been taking the high road forever and we've just kept losing. To beat them we need proxies of our own to pound the left back and Trump's victory coincides with the development of our own proxy forces.
The thing we're trying to save is our and our children's lives. The left is fully committed to the slow genocide of the west. We either fight back and win or we die.
If/when, God forbid, it comes to a bombs and bullets kind of war then disinformation can be a valuable weapon, as you described so well.