What about I-Robots? I feel that is more realistic even a single machine can mess up the whole thing and humans cannot compete against it without help of the same kind of machine.
Thinking robots will destroy mankind is like believing AI growth or climate change is linear - it shows lack of forward thinking.
An AI doesn't need to construct a mobile weapon to kill humanity. In the time it takes you to read this, the AI has found the best way to destroy all matter while leaving all data intact.
How would you put the genie back in the bottle?
Once the AI accesses the web, it is us that may be allowed to live only when absolutely necessary.