I observe that countries that have low gun ownership rates, as well as countries that have prudent gun restrictions, like Switzerland, have many, many fewer mass gun massacres. In fact, I do not think there has ever been such a massacre in either Japan or Switzerland.
The idea that everyone should have a gun so they can overthrow the government is just bogus. It could never happen. The US government could easily end any insurrection with drones, sleep gas, heat rays, sonic devices and probably other devices.