If we lower the birth rate below replacement (roughly 2 children per couple), humanity will die out. This is not a desirable outcome. If the answer is, "well,

If we lower the birth rate below replacement (roughly 2 children per couple), humanity will die out. This is not a desirable outcome. If the answer is, "well, the birth rate will never lower that far, because some people are going to keep having children" -- who will those people be? (Do you presume to be able to choose who gets to have children and who does not?) Aren't those some people then doing a great service, keeping humanity alive? Shouldn't we value their efforts, and give them support? Also, drastically lowering birth rates has negative effects on demographics and economies (e.g. a population pyramid heavily weighted toward the elderly, without enough young people to do the work of taking care of them, or the productive work of maintaining and improving society generally).