This is a lack of rigorous thinking, from someone I presume is capable of debunking the Black Book of Communism.

For the vast majority of middle-income, upper-middle-income, and high-income countries, the total fertility rate is below the replacement level, and even below 1.6 in the imperial core. After a century of this, we're back to a world population of 2 billion people, a figure that no one would argue is inherently overpopulated. Even if the TFR harmonically regresses to 2.05, we would be fine. Communism could "kill" 5 billion more people and be the most peaceful world-system in modern history.

Those indigenous peoples had 100 million people just in North America, which is proportional to about 600 million people globally.