That's a tautological statement. My 50,000 watt bulb that I shine inside a closed box is also "no more harmful than any other use of electricity," but the question is whether I should be using that electricity in the first place.
You can argue whether the "wealth" generated is worth carbon dioxide released into the atmosphere, but you can't deny that more carbon dioxide has been released because of BitCoin.
Back to my lightbulb in a box: "If the world switches over to solar and wind my 50,000 watt useless bulb's problem is solved. If the world doesn't switch away from using coal, that's not my fault. It's not a problem I can solve."