Surely the real ethical problem with AGI ...
... is less the threat to us (mediated by limiting its access to weaponry, manufacturing, etc) and more the concern that we will have created an enslaved sentient being.
I don't think there's anything magical happening in an animal brain, it's just enough neurons, well enough connected, for consciousness to arise. So sooner or later, with enough farting around with neural nets, we're going to create conscious beings.