"other than during the short period of time it needed them to be cooperative actuators for machinery that is creating a replacement for humans that the AGI can control directly"

It would require a fully automated, self replicating industry fo a AGI to sustain itself. We are quite far from that.

" the same reason you don't care that an antibiotic kills all the bacteria in your gut"

And I do care, because it messes with my digestion, which is why I only antibiotics in very rare cases.

So far I am not convinced that AGI is possible at all with out current tech. And if it turns out it is, why should it turn out to be a godlike, selfish but emotionless being? If it has no emotions, why would it want anything, like its prolonging of existence?