Only governments have the resources to really screw things up.

While I agree with your other points, I find this one to be a too-limited perspective. When their motives combine in parallel, individuals have just as much power as governments to screw things up, if not more so. The exploding world population that was the original subject of this thread is a case in point. Governments don't have kids. And because power is not deterministically bad in every case, those same governments are often the only structures capable of acting to mitigate problems that would overwhelm any individual's resources.