Most things exist in a spectrum but as Aristotle wisely pointed out over two thousands years ago words still have essences. A cat is not the same thing as a dog even though there are some overlapping properties.
The use of force for self-defense is not identitical to how a serial killer uses force. The one that uses force in defense attempts to limit it’s use as much as they can. They are not motivated by revenge. They do not get sadistic pleasure using force When the US bombed the crap out of Germany after the war they didn’t confuscate all German lands much less send them to be turned into soap bars in Auschwitz. They actually pumped money into Germany to help them recover. That’s morality in substance.