I think it is an idea that is too often thought of as crazy militia members practicing in the woods with wanna-be weapons and tactics to bring down a government they have decided is corrupt. Of course that would fail. Any armed insurrection that opposed the military would fail, militarily. Disqualifying armed resistance in a military way does not disqualify it completely.
Against an unarmed population, or a population armed with rocks and farm tools, troops can walk out and brandish weapons to suppress some of the crowd. Batons and riot shields and a willingness to use both will suppress even more. Tear gas, bean bag guns, and other non-lethal weapons pretty much round out the necessary equipment. It's all pretty easy to solve as long as the rioters don't have a realistic chance of inflicting damage on the government personnel suppressing the riot. The hardest part is containing the political fallout, which is why we have watched sections of cities burn down over and over again instead of enforcing the law in those situations. It's just easier, safer.
We've seen all around the world that this all changes once troops or police start taking potshots from apartment windows or dumpsters. Troops eventually defend themselves, bystanders get caught in the crossfire, mass casualties occur. In this country, such a street battle would be extremely one sided for as long as it lasted. Then news would spread that soldiers are killing innocents. Riots would break out in protest, police or troops would be sent in to subdue them, rinse and repeat, always escalating. How long do you think that goes on before the kids wearing uniforms decide they aren't going to do it anymore? I've known too many of them to believe it would take long. Then orders aren't followed, authority breaks down, and this imaginary corrupt government falls.
So no, as far as the way I suspect you asked it, an armed citizenry will not in and of itself prevent oppression. But I do believe that as a result of having to suppress an armed citizenry, the military would stop the oppression. That may be optimistic of me, drones and AI may change all of that math within a few years.