"Natural selection has nothing to do with individuals." Very badly put by me, that was. An individual is a collection of thousands of traits (and a lot more than just that). It's the non-random survival of heritable traits that's at the heart of natural selection. Keeping the "unfit" alive is not subverting natural selection in any way. Deliberately propagating traits that would be selected against would be. We call it artificial selection. It has its uses. That is not what the Nazis were doing in the death camps.