Energy use is allocated by how people spend their money. By choosing how you spend your money, you can choose how the energy is produced. If bitcoin is banned,

Energy use is allocated by how people spend their money. By choosing how you spend your money, you can choose how the energy is produced. If bitcoin is banned, then people spend their money on something else. If people buy bitcoin instead of buying a new car, then the net effect on environment is positive, given that car production uses more fossil fuels than bitcoin production.