I think the fear of AI is like the fear of unknown. Machines are programed by humans. If there is any one to fear, it is the programmers because a machine will do exactly what it is told to do. Nevertheless, we know machines do develop faults. If a robot should develop fault (which is likely to be caused by a human), i think it primary assignment will be altered (Mad robot). There are possibility that machines can develop fault but i am not in approval that they should not be used.
My only fear is that human place in the society might be at stake.