The wars of the Imperium against Chaos are nothing if not extreme. That being said... our wars aren't like most wars you may have heard of, from elsewhere. We're dealing with an external force that literally corrupts humanity and makes it into a beacon for the beasts of outer darkness to manifest into the real. If humanity is to survive, we have to use extreme measures.
Yes, I took part in annihilating a city, that much Acumen has correct. But Acumen doesn't take into account the context of things. This city had already used atomics to demolish the Northern Collective, and was on the verge of destroying Vervunhive as well. It was a city full of cyber-altered humans who had been utterly enslaved to a daemon.