It is very possible to bring up edge cases in a productive manner. Expand the conversation to include them. there's no need to assume the first solution idea posted is meant to be the final form
By banning that because it uses "too much" energy now - what are we potentially losing? What developments in renewables, energy storage, or grid development simply won't be there, which we won't know we don't have, because we banned the largest for-profit, skin-in-the-game competitive contest for low-cost energy that the world had ever seen 25 years prior?
Banning it outright is short-sighted. Thinking about it from a higher level is a way of addressing the real issue of carbon emissions while allowing a phenomenon that has the potential to massively help, not hurt, to thrive.
The issue is clearly a tragedy of the commons - the cost (higher air pollution/higher energy costs) is socialized, while the profits are centralized. So the maximization function is cheap >>> anything else. Why wouldn't we expect more and larger coal plants versus research into fusion reactors?
Unsubsidized renewables are already the cheapest new source of energy generation. [0] Even if miners wouldn't be doing direct renewable research themselves, their capital investments into renewables in the name of competition and cost-savings would incentivize more efficient technologies.
In this case the immediate marginal profits from mining are centralized, and the larger benefits of more advanced renewable energy are socialized.
Plus - do you believe that the price of Bitcoin will rise forever? If it did, wouldn't that mean to you that it might be doing something important, to constantly have growth and demand for 100 years? Cuz if I thought so then I'd want to preserve it, not throw it away. Sounds important.
[0] https://www.forbes.com/sites/jamesellsmoor/2019/06/15/renewa...
Even if Bitcoin isn't intended to be "growing forever", the ecosystem can and will.
Shameless hijacking here: at what point will the heat consumption/release rate be so great that the Earth becomes unable to support life? I've seen some back of the napkin calculations that estimate a couple hundred years, at our current acceleration.