I don't believe arming the population will discourage tyrants. Communist governments like Cuba have large segments of their population under arms, maintain large militias, etc and they use these instruments to maintain power, they do not fear them. Tyrannies collapse when the militia, police and army refuse to shoot their own countrymen, not when the citizens start shooting cops and soldiers.

Resistance to tyranny depends on discipline, organization and courage, not weaponry. You don't need a gun to cause job sabotage, stick up placards or make a Molotov cocktail. That's what brings down a tyranny, not armed resistance. Its a great fantasy that we'll be able to arise with our .22s and shotguns and defeat disciplined and heavily armed troops, but it has never happened before in history , and never will. Even in our own revolutionary experience, it was organized conventional armies that finally defeated the Brits, not the Minutemen.