Eugenics need not involve any killing of any kind. While the fastest way of attaining a particular genetic goal would involve lots of breeding and culling the less successful this strikes us as unacceptable for greyhounds let alone people. But until a goal is decided upon and the value of the goal assessed the idea of anybody being in the way of the great noble experiment doesn’t even begin to arise. Killing people is wrong. You don’t have to set this aside to see some prospects of a purpose in selective breeding of our own species.