"There's just enough of me, but way too many of thee" is a prejudice as old as civilization. But it's notable that liberals--who feel themselves shouldered with the duty to run everyone else's lives--regard the rising population as mere mouths and stomachs. That is, as just another problem to solve (or at least to strike a concerned pose about). But the flaw is in liberals' base presumption: that humanity will inevitably rush headlong into ruin without their, liberals', intervention. (They never explain of what finer clay they are made, but that's another story.) They never quite believe that other people can solve problems, that other people can co-operate peacefully with each other, that other people are smart. It doesn't make them feel all affirmed & complete inside, to think that way, to have that kind of respect for other people, as patronizing people does.
Wealthy nations have lower birth rates. So, if liberals are serious about wanting the world's population to come down, they should recuse themselves from economic affairs, so that more people can get rich!