I'm not an AI doomer but, it does not reduce to that claim. The threat is not just one smart being. The threat is beings that and (1) multiply themsevles instantly, unlike humans that take 15+ years (2) share knowledge instantly "I know kung-fu" matrix style. Humans can share knowledge but they can not absorb it like an AI can/could/will. Human armies have conquered other humans. An army with infinite soldiers will win against one with finite soldiers

Yes, you'll come up with all kinds of objections like AI doesn't have presence in the physical world, etc... That's fine. I'm not arguing my example is perfect, I'm only arguing your characterization of one smart being is not the threat being considered.