First point, I have read a bit and I'm unconvinced. People who want kids are having them, if they weren't, it'd be all over the mainstream news. Childless people would be suing Dupont or something.
Second point, again, I agree, but there is an environmental carrying capacity and we keep degrading the environment.
Your third point is true, but I was referring to the increasingly uncertain climate future. There may come a year where there just isn't enough due to an unlucky series of crop failures.
I can't argue against the fourth point.