Monopolies (or even high concentrations) of power are bad, whether that's financial or legal or whatever. However, democratization can redistribute that power back amongst the people. The goal should be to work towards nearly even power, which prevents the abuses in power. If the government was controlled by the people, its "monopoly" wouldn't really be one, because it couldn't be abused by those who wield power within it.

List of governments controlled by their people: ...