The reason the Earth has oxygen at the levels to support human life is purely because billions of years ago an organism called cyanobacteria overpopulated the Earth and caused the great oxygen catastrophe. That's right. It's called the Oxygen Catastrophe.
Is there any actual point to bringing this up? Hadn't heard about the GOE, I think, so I checked in on it. Your overpopulation example, at the fastest, occurred over a period of several million years at the absolute minimum (nearly a billion, possibly even more, at the wider outliers). What our species is doing, and our actions? It's happening over the course of mere millennia. It's literally unprecedented change, and at a speed we've never seen before. The GOE is not really a comparable event, except maybe in the absolute broadest of strokes. What happened then is not a very good thing to pattern how we react now against.
As for the rest... calming down isn't exactly the best idea, really (though it would be perhaps more accurate to call it stopping being willfully blind, rather than something more panic-inclined.). We've been messing with stuff we only partially understand, and most of what we have come to understand is saying bad things at their most conservative, and very,
very bad things not very far past that point.
Life going on isn't really in question, sure. The issue is whether
humans are going still be included in the list of objects still in that set for all that much longer (in a geological sense of longer, anyway). This sort of thing only makes a good movie when it's time lapsed, true, but an end-times of a thousand billion cuts spread out over a half thousand years is still an end-times. From the earth's perspective, things are about to become one hell of an action scene. And
it's probably not going to do anything to make sure the media short it's watching doesn't end up a tragedy (from the perspective of the actors, in any case).
Insofar as effective action goes... we do actually see spats, here and there. Moreso on local than wider scale, and still very sporadic and spread out, but it's a start, and it's growing. Not nearly fast enough, from what we know, but every little bit helps. Not seeing as much in relation to population (and more importantly, population growth) specifically, but
dealing with the consequences improves, piece by piece. But even population issues seems to be becoming more of a known subject of concern. Considering that it's one of the primary root causes of the problems we have... that's good. Acknowledging and addressing the fundamentals of a problem is one of the most effective ways of solving or mitigating that problem, especially over a longer time frame.
And destiny... destiny can shove off. "What will be will be" may be true, but it's no excuse to not try and make that eventuality better than it could have been without action. That things flow is no reason to not swim, especially when the rapids show signs of coming 'round the bend. Destiny is not and never has been reason to ignore the ethical considerations of one's actions... and that seems to be what your line there was suggesting we, as a species, as groups, and as individuals, should do.