Correct me if I'm wrong, but weren't Skynet's "motives" always left pretty vague? IIRC we mostly only know that it was hooked up to a lot of military tech, then underwent a hard takeoff and started trying to eliminate humanity. And "if you have a powerful AI that's hooked up to enough power that it has a reasonable chance of eliminating humanity's position as a major player, then it may do that for the sake of the instrumental drives for self-preservation and resource acquisition" seems like a reasonable enough argument / scenario to me.
Precisely.
In fact, in the Terminator movie and its sequels we never see Skynet or the Terminators doing anything fitting the "evil supervillain" Hollywood archetype.
They never gloat, or curse, or do "evil for the sake of evil" things. They don't even give "Agent Smith" speeches. They just try to get the job done.
http://www.businessinsider.com/musk-on-artificial-intelligence-2014-6
Summary: The only non-Tesla/SpaceX/SolarCity companies that Musk is invested in are DeepMind and Vicarious, due to vague feelings of wanting AI to not unintentionally go Terminator. The best part of the article is the end, where he acknowledges that Mars isn't a get-out-of-jail-free card any more: "KE: Or escape to mars if there is no other option. MUSK: The A.I. will chase us there pretty quickly." Thinking of SpaceX not as a childhood dream, but as one specific arms supplier in the war against existential risks, puts things into perspective for him.