Eugenics is already practiced on a small scale by individual mate selection. It is morally indefensible on a large scale because no existing large scale systems

Eugenics is already practiced on a small scale by individual mate selection. It is morally indefensible on a large scale because no existing large scale systems have the decision-making granularity to appropriately make those kinds of decisions, nor are those decisions relevant to what humans generally need their cultures to accomplish.