What's the point of sustainable resources, stable climate and affordable real estate in a society that fades away? What difference does it make whatsoever?

What if the sustainable population is half of what we have now? A lower than replacement (global) birth rate would move things in that direction in a more palletable way than stochastic murder.

But, Logan's Run could solve population control and balance the Social Security budget. I always wanted to live in an underground city that was a Texas mall. The original mall is gone, but the Houston Galleria has an ice rink, so maybe we can setup there.

You're assuming fertility rates wont rebound once there is less population pressure.