Preposterous logic. Any energy used has to be made up with other sources. The idea that all bitcoin miners are public-spirited eco-warriors is pure imagination.
Rather than venting greenhouse gases produced from the oil and gas mining process, they use it to mine Bitcoin. Sure this results in some CO2, but that's a lot better than venting straight methane.
It's not like excess hydro power in China is stored anywhere. It's literally wasted.. why do you care if people use it to mine bitcoin? How is it cutting in to the energy that other people can use?