I'm honestly in favor of it. Before everyone jumps down my throat, I'm not saying how China did it was the right way.
But we are barreling towards a very unsustainable future. This century is going to be very dire for these next generations. We simply do not have the resources.
There are some great "hacks" I'll call them. GMOs, urban farming, etc, but those just treat the symptoms.
I'm not having kids and this is one of the big reasons why. My family thinks I'm crazy but from my point of view I'm just bringing kids into this world to suffer, so if I do that then it's only for selfish reasons. And with that line of thought I think people who willingly have more than, oh, let's say 3 kids are selfish.
It's harsh, but seriously look around. It's unmaintainable, we can't keep going at infinite growth.
Unfortunately it will never be implemented because there is no way to do it without bias. Sterilizations have always had bias, along race, class, religion, and those I'm against. This is more me yelling into the void "For the love of God stop having kids! You do not need 5 kids! We can't continue with this exponential curve on this one tiny planet!"