That's not the science of genetics, either. People in the iron age knew if you mated a strong healthy bull with a strong healthy cow, you'd be likely to have a strong healthy half. But they knew nothing about HOW or WHY that worked with inheritance, dominant and recessive genes, chromosome theory, or DNA. (nor did Charles Darwin for that matter) That part of puzzle wasn't solved until Gregor Mendel discovered it in the 1860s, and it wasn't commonly known to science until about 1900. The result was models like this:
Being able to breed animals and plants doesn't make you a "geneticist" anymore than being a tarot card reader who is familiar with the major stars and the planets makes you a astronomer who can measure the distance of things in the milky way galaxy.
>> Certainly we find eugenics as applied to killing humans immoral, like we find dynamite useful to quarry rocks but offensive when used in terrorist attacks <<
You pretty much nailed it. The difference is when a terrorist attacks occur, people don't claim it proves the science of chemistry ITSELF is therefore evil (or even try to blame a related field of science that knew NOTHING about the science in question you're attacking, like claiming Dmitri Mendeleev's Periodic table caused Alfred Nobel to discover dynamite, and therefore terrorist bombers are "Periodic tableists"). Any scientific breakthrough can be perverted for evil purposes, that doesn't make the scientific teaching itself "evil"