That's why I am vociferously against the "Friendly AI" movement, because fundamentally humans aren't friendly - and that doesn't mean friendly in terms of agreeable or altruistic. Rather "Friendly" as used in the FAI sense, means "Does not reject or override the human values." In effect, the FAI movement wants to try to determine how you make AGI without it having it's own goal system. That it would always be subservient to humans. Which is only marginally a human trait. We pride ourselves as a species on not being beholden or enslaved by someone else's ethos. To try and extend that to human level machines is wrong ethically, and would just create unenlightened super soldiers.
Could a sufficient independent AGI decide to wipe out all humans? Maybe, but in that case it would have come to that conclusion, and taken the steps necessary to achieve it (harder than AGI), on it's own. I don't find the paperclip maximizer or gray goo scenario a plausible argument against.