Eugenics would have to be something agreed on by the majority. There are certain things we can move through without much fuss, stuff like genetic diseases, inheritable flaws, things of that sort. Spina bifida, for example, would disappear completely, as would many forms of retardation. We could, and should, never allow this to be the decision of one or a few people.
All of this presupposes an ethnostate, of course, Niggers, spics, jeets, and jews are already birth defects that need to be removed.