There are many conceptions of good and evil. Since negentropy is limited, life is always a process of competition, for instance between the cells of your body and your parasites. The holocaust was the expression of a resource conflict; its goal was not to stop life, but to gain control of the resources and societal influence of what Hitler saw as a competing group. Killing was simply a means to an end.
What if your goal is to end suffering? That might well involve ending life, too.