Eugenics has a nasty, Nazi-sounding feel to it. This is partly because we automatically associate it with forced eugenics, or sterilising people, usually women, against their will. Relatedly the other part is the public or group nature of it. Some larger group, from the tribe to the whole society, is weighing in on whether you should have children or not. Some European countries have virtually eliminated Down Syndrome by creating social pressure to abort those children. Sounds like eugenics to me, but I don't hear many Americans complaining about it. Eugenics in America has come to mean not only a belief in racial differences, but that noticing said difference proves one believes in superiority and inferiority and wants the bad ones to have fewer children. The evidence for this is emotional, not logical, but that is often the case with political words.
Update: Donna's comment reminded me of a section to go here. In addition to whoever the bad groups are that eugenicists want to have fewer children* - in the case of the Nazis it was Jews, Slavs, Gypsies, and let's-ignore-for-now-that-the-Japanese-are-quite-Asian - there was the Teutonic ideal of building Ubermenschen actively promoted as well. It gets creepy, and as Donna hints, can be rife with contradictions. It is also often bad science when it gets that far, as people pretend that they know for sure what would be good to have more of and what to have less of, and what the side-effects of that are. If you like science and general cleverness, for example, the Jews are a poor choice of folks to have less of.
Yet in small private ways, eugenics is what we all do at some point in our lives. We decide to have children or not, and we choose a mate. Even if we think we are choosing that mate on the basis of environmental factors, evolutionary biologists claim, with evidence, there is a lot of guessing at the genetics in our decision. Symmetry is considered more attractive, and is also a sign that there are fewer deleterious mutations. Other aspects of beauty can be tied pretty quickly to child-bearing, rearing, and protecting abilities. We usually notice what our mate's family is like, and older generations are likely to stress, from experience, the importance of Good Family. Whenever there is hand-wringing that educated women aren't having enough children - the men are less-often blamed - that's essentially an argument for eugenics. Social pressure isn't the same as holding a gun to someone's head, but it has an effect.
It used to be considered selling out for a woman to go to college in hopes of finding a husband. Dunno about that. I hoped at college to find an intelligent wife who was interested in having children. Seemed a perfectly good motive to me. (We succeeded in that.)
I have a parallel experience. "Shock treatments" had an equally nazi-ish ring to it, which I carried in my head when I started working at the state hospital. We no longer performed ECT's then, nor the deep-insulin shock treatments that had also been practiced a generation earlier. I gradually learned from older psychiatrists however, that the treatments often did work, and not everyone had the terrible memory side effects of reputation. Later still, I learned that much less electricity was now used, that treatments did not have to be bilateral, and that there were ways of identifying problems and ceasing treatment much earlier. ECT's are very good treatment for a lot of people, and the only treatment that works for some with depression. It is used on pregnant and nursing women so that no chemicals enter the bloodstream.
I've been through this once. People having worries about nazis doesn't mean that any actual nazis are involved.
No one's going to change their meaning of the word just because I think their usage is imprecise, but it pays to notice that "eugenics" means a lot of things, not all of them evil.
*Also, homosexuals and disabled people of many stripes. Useless eaters, they were called.