It's understandable that a government would have plans in place should its citizens become a threat to themselves and others around them. I think many wouldn't find that unreasonable. However, and it's slightly off-topic but relevant to this, what I do have an issue with is armed force against unarmed and peaceful protestors.
Case in point: the whole FBI assassination plot conspiracy where leaders of the Occupy movement in Houston were targeted for assassination. In my opinion, that's where the use of force crosses the line.