Pyrogenic dons his double breasted devil's advocate suit...
"On darwinian grounds, this is false. Taken strictly as a problem in natural selection, it would seem the altruism of caring for people is selected over the more brutal efficiency of not doing so. To argue for a dysgenic danger you would have to say that cultural evolution was overbalancing genetic evolution."
Isn't that the dysgenicist's point exactly? That new factors such as medicine and more abundant resources have allowed our altruism to halt natural selection's pressure on our species?
In the past, indeed for most of human history, the pressures you describe may have been selecting for altruism. But modern technology has warped its benefit. A dysgenicist might point to the proliferation of asthma and near- and farsightedness as signs our altruism is backfiring. Many asthma sufferers would never have survived childhood in the past, but now survive (the altruists cheer) -- to pass their possibly dysgenic trait to their offspring (the dysgenicist cries for humanity).
(Stay with me here as I take this a bit beyond strict genetics.) Think about birth control and family planning: doesn't it strike you as odd that the more educated, richer, healthier, or more successful you are, the fewer children you're likely to leave behind? A dysgenicist points and says that's why the gap between the rich and the poor gets bigger, everyone would be better off if we controlled the proliferation of the poor.
The fact is, cultural evolution has negated a good chunk of natural selection once you've made out of the womb, at least in developed nations.