I'm not sure that's true. Look at our murder laws for example. We have several different degrees of murder severity, depending on planning and forethought. In some cases murder is even downgraded to voluntary manslaughter where it legally is no longer considered murder. Causing the death of another human is hardly a black and white issue.

In short, a reasonable person could argue that removing certain people from the population is the best course of action. You and I may disagree, but this other person does have some rationale to back up his/her argument.