At a minimum, they could refuse to take proof of work currencies.
Even so, if the root problem is clean energy, banning crypto is only going to help until the next energy-burning tech comes along. i.e. we'd just be kicking the can and destroying digital currency in the process.
And then there is the whole distributed Ponzi thing and going around financial regulations thing that enables endless crime.
It's a really shitty technology used for really shitty things by a lot of shitty people. Not much more to it.
Allow other financial firms to play by the same rules and instant transfers around the world will be close to free. POW blockchain just isn't very useful for any real problems we have today other then evading authorities/regulation. It's good to hear more people speaking openly about it. As anyone who tried to argue against MLMs/pyramids and other scams learnt it's a thankless task.