Most of all, when people say "don't have kids for the environment" it actually really hurts environmental action. Pretending that self-sacrifice is inherently environmental action, that we will save the world through sacrifice, is just one of those weird ways that Christian religion has worked its way into people's every day life.

We save the climate by stopping ALL emissions, and then also in the later half of the century actually sequestering CO2 at a pretty consistent rate. We don't get to that by halving the population, that's not a solution in any way. It's not going to be easier to get to zero emissions with half the population, if anything it's going to be harder. And we definitiely won't be sequestering CO2 in the later half of the century if we're dealing with all the challenges of reducing the population by any significant amount.

I'm willing to wag my finger at you, not about sacrifices, but falsely equating climate action with sacrifices. Climate action is one thing and one thing only: reducing emissions and eventually reversing some of them. It is not sacrifice for the sake of sacrifice.