> that energy can be used for something productive

A decentralized/borderless/censorship-resistant/virtual currency is one of the most productive things we can use energy for. It might not be as apparent in the US or the developed world, but Bitcoin is a life-saver for many people in countries with crumbling currencies. We waste a lot of energy on things that are far more more useless (like christmas lights for example[1]).

We should just put carbon tax on everything with environmental side effects and let the market decides what's a productive use case vs one that isn't.

1: https://bitcoinist.com/bitcoin-mining-energy-consumption-us-...