I used to think this, but here's the problem: new resources to extract mean absolutely fuck all under the current global paradigm.

There's enough iron out there to make several tons of it available to every human in existence for whatever they need or want to do. Will that happen? No. It's not profitable for the owner class to do that. Instead, they will fight amongst themselves until someone has an effective monopoly on asteroid mining, and then limit the supply so they can generate maximal profit (De Beers, anyone?)

We have the capability, right now, to feed everyone on Earth. To clothe everyone. To house everyone. We don't. Any resources out there that we might find useful will be gated behind the same greedy, psychopathic group of leeches that currently control everything else.

The planet isn't being destroyed because we had no choice. The planet is being destroyed so a bunch of MBAs could show off a nice graph at the quaterly meeting. It is very much delibrate. Any resource extraction in space will solely be done in that it is more profitable than doing it on Earth, climate be damned. We need to fix that problem before asteroid mining for the good of Earth and humanity is even an option.