The strength of the reaction is, I think, mostly due to its being situated among artist communities, who tend have a very strong, swift moral consensus formation process and a fairly strong voice. 

Artists see themselves as adepts in the plane of narrative, anthems, banners. Ethereum's power consumption is funded, primarily not by transaction fees from real commerce, but by speculation and the minting of mining rewards. These things only have force because a narrative has been constructed where the network has value. Artists are aware that their participation would be constructing a large portion of the value attributed to the ethereum network, far out of proportion with the costs of the transactions involved, they would be selling the network legitimacy and narrative force. The consequences of their actions would be very real.

I'm not sure that many people who propose this evaluation would support its inverse implication - that there are uses of fossil fuels to generate mains-grid electricity that are non-problematic and worth the environmental damage, given the option of renewables.

I think they'd mostly say that the sustenance of human lives under modernity (running hospitals, etc) is necessary and that the side effects of living normal lives (transport emissions, food production emissions, whatever ya gotta do to pay rent) is at least understandable and forgivable, while inventing this new category of emission is something very different.

The ones standing at the epicenter of the reaction do all know that there is a lighter alternative to Proof of Work, they know that it really is unnecessary, that most of this is all a consequence of running fast and breaking things and that there is yet little else to show for it.

They know about Proof of Stake, but you wont ever hear those people singing enthusiastically about Proof of Stake, because they have no enthusiasm for anything in the space. I think you're right about "Many people have soundly placed cryptocurrency within the "bad thing" box". When genuinely good applications start to emerge, these folks will be slow to notice, but I find that totally understandable: So far, despite all of the innovation and all of the investment, I'm not aware of a single application (other than remittance) as of early 2021, that's doing any material good for the world, I only see speculation, experimentation and foundation-laying, so far. I'm not saying there really aren't any good applications, it's noteworthy just to say that not a single one has found its way to me. Very soon I think some genuinely good things will start to emerge in the Cardano ecosystem, and although they are very real plans (banking the unbanked, building identity/credit score systems in the developing world), and I have complete faith that they'll come to fruition, they're still just plans, there isn't anything I could show to one who was angry about what has passed so far, that would calm them.

But this is a somewhat puzzling response. Surely, if your issue is with greenhouse gasses and environmental damage, criticism should be directed towards things like using fossil fuels to generate that electricity. 

NFT's don't cost a lot of Ethereum for a good reason. They cost a lot because Ethereum is slow in adopting proof-of-stake. 

I think it's very valid to argue that instead of deploying NFT technology Ethereum should have first moved to proof-of-stake. 

Intuitively, we might imagine that the issue here is that people perceive the use of electricity as "wastage" and therefore not worth the negative environmental impacts of other, more justified usages. 

Using outdated proof-of-work technology instead of more modern technology is wasting energy, the same way that using the old lightbulbs that need more energy then the newer more efficient one's is wasting energy. 

Did you know that the US energy grid wasted 67.5% of the energy produced in 2019?

That doesn't matter as electricity is something we want to consume 365/7/24. It would only matter if mining would stop whenever the electricity production is relatively low but that's not how the mining pools operate.

But it does imply that we have a huge amount of optimization to address through building smarter electricity grids, building more optimized energy markets, and rolling out innovations like smart-meters and battery storage. 

While it's possible that such technology can be used to optimize the energy marked it doesn't imply that the technology is enough or cost-effective (it's also possible that the problem is week to week or month to month energy flucutations). 

You're right that a negative affect to NFTs in particular / blockchain stuff in general is part of the reaction, but I don't see the reasoning error in

• "<X> causes greater electricity consumption;
• on the margin, greater electricity consumption currently causes <more pollution / finite resources to be consumed faster / more birds to die due to windmills / ...>, which is bad;
• this is a downside to <X>."

It's probably the case that NFTs do not directly cause greater electricity consumption, but NFTs do plausibly indirectly cause greater electricity consumption, e.g. via making Ethereum more valuable, thus increasing mining rewards, thus increasing competition.