I agree with your points, and how I interpret "natural" has nothing to do with how often an individual does something. Many humans drive their cars every day. Does this make it a natural thing to do? I can see a definition of the word that makes it so. Still, the way I see it is that driving a car is something very unnatural to do, even if many people do it every day, but killing humans is something very natural, although most humans will never do it.

Most people will absolutely kill another human if the circumstances call for it. It's in our nature to do so.