I assume you are referring to issues related to this:
Sierra Club - Wikipedia
I'm not familiar with that history but the Wikipedia summary doesn't mention "genetic cleansing" or "sterilization". I can imagine there could have been anti-Mexican racist elements to that or it could have largely been driven by concerns about overall population levels (or a mixture of both).
I should probably read Paul Ehrlich's book "The Population Bomb" since I've heard about it and I'm interested in 1960's history. Knowing nothing about what it actually says, I agree that the huge world population booms in the last 100-200 years are a serious issue.
We have managed to temporarily avoid the past predictions of starvation by plant genetic modification, and huge uses of fertilizers and pesticides but there is likely a limit to future productivity gains. Meanwhile, populations continue to surge. Also, this hasn't avoided the inherent related increases in carbon emissions and ocean fish populations are being devastated by overfishing, pollution, and acidification via carbon emissions all of which are significantly linked to human population levels.