It is true that the climate is used frequently as a convenient weapon against things people don't like politically, but this is a real issue.
I'm a huge proponent of crypto currencies. I rail against the abuses from central banks like the Fed, and the evils of using a currency to engineer control over free people. I point this out so you know I think crypto currencies like Bitcoin are super important.
But if we destroy our climate/environment, crypto currencies aren't going to feel like a big deal. We have to care about it.
There are alternative models. One of the reasons I got into Eth was the work on proof-of-stake over proof-of-work they were undertaking.
As proponents of bitcoin I think we do ourselves (and bitcoin) a disservice by dismissing climate-based criticisms. Sure the messenger may not be sincere and with the best of intentions, but lets take the argument seriously regardless. If there are problems with the argument, let's address those rather than question the credibility of the messenger.
Aluminum production and datacenter operations also use a shocking amount of energy. Apparently Argentina uses a lot of electricity. People complain about bitcoin specifically because they don't recognize any value and they're frustrated that other people disagree. If they were genuinely worried about environmental impact, they'd look at the externalities of electricity production & distribution in a more general way (cap & trade? carbon tax?) rather than arguing that one particularly visible use of electricity is immoral.
Alcoa owns 24-26% of a very large hydroelectric dam in Wenatchee Washington. It’s more profitable to sell their power shares then to run their plant, so the largest(also one of the best paying) employer in town shuttered their plant to sell power instead.
There are also economic impacts not just ecological.