In the comments below Jason says in regards to the connection between eugenics and genocide and the "slippery slope":
In your current comfortable first world circumstances, you are right the slope is perhaps not that slippery. I hope you are never tested in a less comfortable setting as then I think you might find it can be pretty slippery after all.
A reference to the interlocutor's status as a citizen of the comfortable First World (which itself is a somewhat archaic term by now I think) seems de rigueur in many arguments. And I think many people will find it plausible that someone in an affluent consumer society would be blind to the "dark side" of eugenics, and how it could lead to genocide. But I think this plausibility is entirely superficial, and collapses upon closer inspection. Rather, it is I believe in "First World" and advanced nations where the likelihood of the ubiquity of eugenics and possible genocide predicated on systematic eugenics is going to be the most probable outcome. There is a large general issue at the root of this confusion, the implicit progressive "Whiggishness" in our sensibilities, which derives in part from the power of science to advance in a clear fashion. This sensibility has some grounding in our contemporary realities, but we take it too far. History can, and does, move in cycles. In the 18th century the most articulate and crisp racist sensibilities were arguably elucidated by relatively secular forward thinking intellectuals such as Voltaire, David Hume, and Immanuel Kant. This seed of scientific racialism waxed and reached its peaks in the years around 1900, before waning in the 20th century. This complex reality is often not appreciated when we Americans consider the arc of history moving always forward as the arrow. Similarly, because of the Whiggishness of our conception of cultural change many Americans have a hard time wrapping their minds around the fact that between 1837-1841 the the Vice President of the United States, Richard Mentor Johnson, was known to have had common law mixed-race wives, with whom he had daughters who he acknowledged. Johnson was the nominee of the more racially populist party of the time, the Democrats, to boot! This would not have been conceivable in a few generations, when despite the outlawing of slavery the racial boundaries were much more finely and sharply demarcated. This Whiggish tendency means that when it comes to barbarities "less developed" societies are perceived to be more susceptible to breakdowns in civilization. But that's just not true. People are regularly surprised that in
much of Asia economic development is correlated with sex selective abortions.
That's fine to be surprised, but this seems to be something that's replicated in both China and India. So on to the specific point of personal eugenics, it will be societies where there is personal wealth, as well as a demographic transition, where the means of reproduction will become a major public policy and individual choice. These are also the societies where medical costs are far more socialized, whether directly (e.g., through single payer or national health services) or indirectly (e.g., requirements that no one be turned away from the emergency room). When health care is socialized it seems that there is the strong possibility that society will feel that there is an incentive for it to become active in the shaping of the characteristics of the citizenry. In contrast, in underdeveloped societies where health care is not a right and the population pyramid still skews toward youth, finely-grained eugenical sensibilities won't be necessary, there'll be a surplus of humanity. All this is not to say that I think that the "end of history" will be toward some eugenical regulatory state, at least in the medium term. Rather, the necessary preconditions for this sort of society exists in the developed First World, not the less developed Third World.