Can't tell if you're disagreeing with OP but they weren't arguing that procreation had any inherent good, just that it "is".

Under most circumstances you can bet that any given person would choose life, even in the face of extreme pain. If that person were to change their mind however, euthanasia should be an option, and that I could see an argument being made for it.

Now, to go back to nature just being what it is without morality, the argument that we're destroying the environment doesn't hold up when you remove people from the equation. I mean, sure you might actually fix a bunch of ecological problems from our current point of view but once we're gone, that value system ceases to exist. Earth doesn't care if there's blooming biodiversity living on its back or that the entire atmosphere might be filled with toxic smog. Those are only problems because we say they are problems.

To go and end the entire human race for that is probably the least likely sequence of events we can fathom. We're hardwired to survive, and I don't see that changing anytime soon.

But what defines goodness?

That was my response to the question -- calling something "good" or "bad" is a moral judgment. Try applying the arguments to any other species, which do not construct moral systems, and it should be obvious why calling procreation morally wrong or bad makes no sense.