Has the armed civilian population done anything to protect constitutional rights? Last time a section of them mobilized, it was to overthrow a rightfully elected government.

They were unarmed and the government was and continues to be scared shitless of that "attempted overthrow" (with no weapons? Does anyone really believe that had any chance of succeeding?) to this very day.

Seems to me like that Second Amendment thing could be very effective with a sufficiently motivated population.