Actually useful is subjective. What's the carbon footprint of all the gpu rigs in the world used to play video games? Is that useful for you?

Although I might disagree with the use of the word "fascist" here, I don't think that's an entirely fair comparison. Societies usually ban things that are directly harmful to someone else (or in some cases to the person themselves), and burning trash in a populated area falls under that. Indirectly harmful things could also be banned, but the consumption of resources alone usually doesn't satisfy that in a liberal society unless the resource is rather scarce. (Think water during drought.) In other cases, use of resources and other indirectly harmful things just tend to be taxed.

A better comparison might be banning driving for no objectively useful or socially acceptable reason.

I can see how one could deem it kind of totalitarian if driving for no purpose were legally banned. Add in the fact that many people here probably take computing personally (as do I), and it's no surprise that it will seem totalitarian to decide which kinds of computation you can use your resources for, regardless of whether the computation actually makes any sense to an outsider.

edit: word choice