The burden of proof of the problems of overpopulation is on you. We don’t have to prove that there is a “right” population for the earth. You do. And I don’t think you can. Malthus was proven wrong many, many times.
I don’t know what the right population is, if there is one. I just know that where we are headed is not right, and nothing constructive will be done to stop it because so many people won’t admit there is a problem or can’t see it.