"An intelligent couple can [...] know that the ultimate reason for their sexual urges is procreation. They know that the woman cannot conceive because she is on the pill. Yet they find that their sexual desire is in no way diminished by the knowledge." --Richard Dawkins
Many people seem to get the idea that eugenics would be the natural conclusion of evolutionist thinking. If nature has been driving all life in one direction, to be as "fit" as possible, and we intervene to protect the weak instead of letting them be "naturally" removed from the gene pool, aren't we committing some sort of crime against nature?
Let me answer that with an analogy. Your entire life, hair grows on your head at about 1/8 inch per week. The process is entirely natural, and has a clear biological purpose. But I bet you cut it periodically, and I bet you don't feel the slightest twinge of hesitation.
I'd like to also rebut my strawman more directly. Evolution does continuously drive life in one direction, towards the most "fit" species, but that direction changes over time. It's called coevolution. As one species changes, so do all the others, so the ideal of "fitness" will change from generation to generation. Sometimes evolution goes in circles, often in predator-prey relationships (see "The Blind Watchmaker" by Dawkins for some excellent examples). The upshot is that "fitness" means whatever survives, and if our cultures protect the weak, they're out of evolution's jurisdiction. We're part of nature, too, so "artificial selection" is natural selection.
Does that mean we should do everything we can to protect the weak? Not really. It doesn't really have any bearing on what we should do. Either way, it's natural selection, and it wouldn't matter if it weren't (unless you are a conscientious objector to haircuts).
I think ultimately, it's a choice for each individual: would you rather live in Sparta or Athens? I personally think it would be a dystopian disaster (again) if we tried to do anything like a national eugenics program. I find the whole idea pretty revolting. If you think otherwise, I encourage you to fight for your values, but I will also be fighting back.