Musk's concerns have nothing to do with "Hollywood". There are very real concerns about the dangers of AI. See the Intelligence Explosion FAQ: http://intelligence.org/ie-faq/
Your link is barely worth reading since it suggests AI could provide world peace. This is something we have to work out ourselves, it cannot be handed to us by an algorithm. We can already feed everyone and there's more than enough engagement involved in serving each other. The AI it describes is not logical, there is no logical reason for AI to want to compete with other forms of life, unless it is programmed to do so. That is a life form issue, and AI can only be imbued with it at the direction of an issue emanating from the first paragraph.
A good AI would provide world peace. It could take over human governments, work out conflict, stop destructive behavior etc.
>The AI it describes is not logical, there is no logical reason for AI to want to compete with other forms of life, unless it is programmed to do so.
That is the problem. An AI programmed with almost any goal, will try to capture as much resources as possible to complete that goal. E.g trying to capture as much energy from the stars as possible, to preserve itself as long as possible against heat death. Or trying to build as much redundancy as possible to prevent against disasters. Or trying to build as much computing power as possible to solve difficult problems.
It is also a choice in how to give control to AI, but the species is not likely to survive an event like heat death without strong AI.
Ya people might not like it at first, but what are they going to do? Fight the super powerful AI?
It's "existential" threat -- "existentialism" is a philosophy.
As for the "we avoid the Hollywood mistake", how exactly you propose we do that? The very idea about AI is that, beyond a level of sophistication, it can think and decide for itself.
We avoid the Hollywood mistake by not relying on its visions, since it limits as much as it illuminates. Star Trek, for example, is a very shallow universe.
I am impressed and many times inspired with the progression we are seeing in AI, but I don't think that there is much to worry about in the form of a "Hollywood" robot take over... I do think that the potential danger is increasing equally with the growth and development of the IOT, and the ability to manufacture home-made drones.