Ghandi led a non-violent resistance that helped end the British rule in India.

Anyway, the idea of the state's monopoly on violence is that all others can settle their disputes without violence. That works pretty well in my experience.
Of course this monopoly has to be controlled and restricted, but there are better ways than arming up.

You seem to be pointing at the scenario that the monopoly goes completely rogue and it is used to violently suppress the population. Other than that I don't see why state actors use guns against innocent people. At least not more than a random person with a gun.