I see population control as a necessary global undertaking somewhere down the line but it comes with some troubling moral consequences. In China where no fucks are given about ethics they just instill a one-child policy. In first world nations there seem to be the pressure to not reproduce because of economic pressures and I can't help but feel this is the wrong attitude.
But alternatively there are population booms happening in countries that are still developing that probably need something done about before it creates more problems by having a large population of people with low prospects. Think Arab spring and refugee crisis. I think it's ethical then to start handing out contraceptives as a part of foreign aid
What I like about One Piece is the insane amount of worldbuilding and the amount of cultural influence Oda draws from, well, everything