The problem here is that everyone can choose the green method but won't use it because it won't give benefit to them. They rather choose the dirty cheap method that would somehow going to affect the climate change. To cut it short, people like these doesn't really care about the environment neither the climate effect of what they were doing. It's like if the other countries can use why can't we can and the process of destroying earth is still going on. They only care about what could benefit to them despite the fact that they were slowly destroying the environment. Bitcoin has nothing to do with this crap since we all have a choice what power source we should use.
The thing is that much (I don't think that it has been quantified) of bitcoin mining is mined using spare power - e.g. power that would otherwise be dumped. E.g. a hydropower station might produce X, but only uses .9X much of the time so that extra 10% would just be lost or wasted, not stored.
So there are plenty of either intentional falsehoods because people don't want bitcoin to succeed because it will remove some of their power or there are people aren't fully informed who are reposting inaccurate information.
(Proof of) Work provides security to the blockchain. If you compare, say, the total cost and total carbon footprint of the requirements needed to secure the Euro, the Dollar, the Yuan, or Ruble, you would find that they each vastly dwarf bitcoin. What is needed to secure the US, China, Europe or Russia and hence their currencies? (See e.g. nothing at stake etc). Physically printing currency or electronically creating it is not the only cost. Without the ability to protect itself any of these places would be overrun and the currency - since all are fiat - would become worthless.
