The idea of SAI is that it progresses at a significantly faster rate than biological processes can. For example, if humans and chimps were on a "staircase of evolution" and were one step apart; SAI would be one step above us a mere hour after it is turned on. After 2 hours it would be multiple steps above us. So the theory goes, anyway.
This means that evil aliens would be unlikely more dangerous than evil SAI.
Not that he's suggesting we announce our presence to aliens, merely look for them.
