Scott, you are backtracking. Maybe the truth is that no scalable QC is possible. It seems to me that either (1) scalable QC is a consequence of currently established physics, and will be demonstrated someday if civilization does not collapse; (2) scalable QC is a speculative extrapolation of current physics, and its possibility is a open question; or (3) current physics is fundamentally wrong for reasons that are not understood. I thought that you were in camp (2) but now you seem to be in camp (1).He justifies quantum computing research as being objectively important because he says that an "advanced extraterrestrial civilization" would be doing it also.
I say that scalable QC is an open scientific question. It might be true, and it might be false. Aaronson does not seem to want to accept the idea that it is an open question. He will agree that no one has shown it to possible, but then he will deny that it could be impossible.