That proves the point though that cheap green energy sources are not plentiful.
If you think that there isn't enough available to power the bitcoin network, that's an issue for those concerned with the network then. Let those stakeholders worry about that.
Most of the bitcoin is done in China using dirty means as is most manufacturing,
See the chart I posted a couple of days ago. Bitcoin mining is in its infancy but already it has a far higher green energy concentration than other activities.
but at least manufactured goods are useful, essential products that by and large we can't do without,
Essential? You mean all that cheap, plastic crap that is bunged into containers and sent to N.America and Europe? You say its essential? I say that the current monetary model encourages rampant consumerism - resulting in people buying a whole load of crap that there's no way in the world they need. This - is at the heart of the energy debate - not bitcoin mining.
Over and above that, see my post from the weekend with the comparison of btc mining energy use vs. gaming. You talk about what is essential. How is gaming essential? It uses a hell of a lot more power than btc mining. Furthermore, btc mining is far more progressive in utilising far more green energy sources than gaming (and as far as I can see, most other activities).
I'm sure horse and cart owners said the same thing when car use was at an embryonic stage.
we can live perfectly well without it.
If you want this inequitable financial and monetary system to continue in its current form, that's your business. I don't. Henry Ford identified these shortcomings 100 years ago already. Change has been a long time coming.
Surely we should be using green energy like in Iceland for essential useful product,
What's this "we" business? How much have you invested in green energy infrastructure? Bitcoin mining is a tough business - that now requires major investment and a commitment to that business over the longterm (if those guys are ever going to see a return). They're stumping up their own money to fund these projects. Therefore, why should you have a say in that?
You can claim that its boiling the oceans yet anyone who claims that - do you see them calling for gaming to be outlawed? Do you see them calling for people to stop watching cat videos on youtube (youtube in isolation accounting for a horrendous amount of energy use)? Cat videos and gaming are essential too, right?....whereas the global, permissionless, uncensorable, real-time final settlement system that is bitcoin isn't. Makes complete sense.
The reality is that the people who roll out this argument are diametrically opposed to bitcoin. If they weren't they would suggest we're ok with it if it uses wasted/stranded/renewable energy. But that's never the line that's taken.