They are actually quoting Paul Ehrlich as an authority. *facepalm*
With the terraforming capabilities we’d inherently have as the population grows, we could easily sustain a trillion people on earth (think of it basically being transformed into a multi-level giant space station, with large spaces for wildlife, agriculture, etc. with nuclear fission/fusion power). The people spouting about a “sustainable” population smaller than what we have today have absolutely no imagination and are stuck in a Malthusian mindset that has proved ludicrously wrong for centuries running.
I know. Its like they never seen The 5th Element or Star Wars.
We have all this WTAER on the planet, just begging to be populated!