Also though... How hypothetical is it? Besides all of the humanity based history where radicals get control of government power and guns get turned on citizens... We've also watched sci-fi television and film become sci-fact/sci-reality in tons of examples. Why wouldn't AI deciding humans are the problem and it is the solution not be something to worry about?
And you have to take into account all of the examples of science fantasy that has become reality before answering.
The only logical conclusion one can come to is that it is something to worry about when taking into account all of the examples AND human history.