Nuclear weapons are an existential threat - that's why there are layers of human due diligence. We don't just hook it up to automated systems. If we hook up an unpredictable, hard-to-debug technology to world-ending systems, it's not its fault, it's ours.
The AGI part is Elon being Elon, generating a lot of words to sound like he knows what he is talking about. He spends a lot of time thinking about this stuff when he is not busy posting horny teenager jokes on Twitter?