This one differs from the previous one in that its conclusion does not ultimately lead to antinatalism, but I hope that you see, as I do, that its conclusion is altogether ridiculous as well.
Let us start out with a simple little argument. What would you say is a morally good thing? Giving to the homeless, lending out money, helping a friend in need? Let's go with the first one. Now pretend we live in a better world - a world where everyone is moral and kind, you know the drill. Would homeless people even exist? The world would be so full of giving, sensitive people, that it'd ultimately be quasi-communist. But this isn't an argument against Communism. What I'm trying to say is, isn't that world a better one that this one? Isn't the world where everyone does the morally righteous thing a better one where only a select few do?
Now starting with such things as helping each other out, this statement works fine on most of the morally 'right' things we test it on. But if you take having children as being the right thing to do - then we run into some problems; in a world where everyone does the morally right thing, Tokyo city would look like a ghost town. There would ultimately be so many people that everyone would be poor, there wouldn't be enough food to go round, and people would be literally climbing over each other to get to places. Overpopulation, thy name is justice.
The problem here is that saying that breeding should halt at some point is akin to saying that we should stop giving to the poor at some point; the whole thing makes little sense if we take breeding to be a morally righteous thing to do.
Comment if you think you've proven me wrong; I'm sure you have, I thought this up after my latest bout of mild-ish insomnia.