Factually untrue!
Obtaining resources on Earth generates pollution that stays on Earth. If we move mining off-world, the byproducts of mining don't go into streams, soil, etc.
Furthermore, generating energy in space and beaming it down to the planet means not having to burn coal, reducing the risk of nuclear accidents, and eliminating the need for dams that disrupt ecological systems.
Yes, we'll need to burn more fuel to get there, but that's the nature of progress. The other alternative is to fall back to a pre-industrial lifestyle limited to only those parts of the globe where the temperature is mild year-round - unless you want to keep burning wood for heat in the winter.
What, did you think there are no byproducts from operations done with raw resources AFTER they are mined?
And how about the mere transport of resources?
As for the Carbon - it doesnt matter how slowly we do it, we will still remove it all from the ground. It is a non renewable resource. Look at what we've done to slowly renewable resources like species - how many have gone extinct in the last 100 years? So yeah I think with carbon it's a foregone conclusion that we will floodthe atmosphere with it. But non biodegradable plastics etc. at least we can phase out.
And I understand the concern, but if reducing CO2 emissions is the goal, the first targets should be the production of electricity, heat, transport and agriculture. Food gets transported nowadays by airplane and maybe we shouldn't shut down nuclear power plants to replace them with coal plants. Plenty of low hanging fruits if you ask me.
We can find lots of resources and turn them into useful energy and things.
But that only exacerbates the pollution issue, regardless of where we obtain the resources. Especially noxious is the non biodegradable pollution and the millions of years worth of carbon released from the ground.