The foundation of Civilization's second-order utilitarianism, as taught in their schools, is that—among other things—being cautiously nice isn't supposed to result in your loved ones being shattered in Hell and you having helped an endless-torture dimension to conquer your host planet. Being cautiously nice isn't always supposed to result in the locally best outcome, maybe not even a good outcome, but it's not meant to result in that. If it does, surprising you, maybe you were wrong about something.
(Though this Keltham will still, to the very end of this timeline, never explicitly break any explicit oath that he has made. He will never stab anyone personally with a knife, will not harm anyone in any way that would be effective for somebody inside a physicalist universe and hallucinating. Just in case he's in dath ilan and insane and dreaming all of this as his brain's excuse to violate deontology.)