What you must also mention is that electricity is a finite resource. Consuming electrical energy - even at a hydro power station - means the energy you used isn't delivered to somewhere else.
you might say that the grid can only support a certain load at a some given time, but obviously more energy could be provided.
in any case, i think it's silly to concern ourselves with (specifically Bitcoin's) energy consumption, as it's tiny compared to the efficiency gains that are realized elsewhere as a result of bitcoin's adoption.