Antinatalists claim that it is immoral to procreate. For instance:
David Benatar argues there is an asymmetry between pleasure and pain, which means it would be better for humans not to have been alive:
1) The presence of pain is bad;
2) The presence of pleasure is good;
3) The absence of pain is good, even if that good is not enjoyed by anyone;
4) The absence of pleasure is not bad unless there is somebody for whom this absence is a deprivation.
It comes down to: the less unhappy people there are the better for society as a whole (and presumably for the people that don't exist).
But if the morally minded should subscribe to this ethic, it will mean that subsequent generations would be composed of less and less people reared by the morally minded. Given that the purpose of ethical values is to promote harmony and well being, it follows that in a society composed of a higher percentage people raised by the lesser morally inclined, there would be at greater amount of discord and unhappiness. Thus having children and raising them to a high moral standing is a greater good than refraining from procreating.
So the question is how do antinatalists answer the global effects that "the good people dying out" can have?
Here is the assumption that, a child will be morally inclined much as those who raised him, but I believe this is empirically backed.