When people say "overpopulation" they mean in the Malthusian sense that there are too many consumers and not enough resources. Malthusian ceilings still exist, but ever since the Industrial Revolution countries have managed to push it up with technology (more efficiency, more output, less waste, etc.). So, theoretically it's a thing, but realistically it's not a concern.
So someone is making some determination of "too many". Then someone is determining how to cull the population (in our case, it's an injection of a poison). Then someone is determining how to maintain a certain level. China was doing that and really fucked up their population causing families to kill off their daughters. Sick shit.
Industrial societies haven't been very good at realizing technology and market forces have broken and will continue to break the Malthusian cycle. Nor do many people realize how fast birthrates are declining (even outside the Industrial world young countries are aging quickly as they industrialize).
A lot of well-meaning people think our planet holding 7 billion is dangerous without thinking about birthrates or how population growth is seriously slowing, so they demand immediate government action without thought to how people can sort out their problems.
Pretty much why young people love socialism: it's easier to see every problem needing government action rather than let emergent resolutions arise.
I tend to go with one of Isaac Arthur's (youtube.com) irritatingly positive outlooks on humanity that Earth could support a trillion individuals, if only humanity would get its shit together.
Edit: figured I should add the link
Niggas produce so Niggers can eat
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