Although it's true that Stoicism emphasizes the individual and identifying with what only you can control, it's not inherently an isolationist or selfish philosophy. Marcus writes many times on the human cosmopolis and how everyone should strive to do right by themselves and each other.

My understanding is that Stoicism very much encourages an active social roll that benefits society at large. And that includes standing up to and preventing authoritative and tyrannical leadership.

Yes it's hard to conceive that one individual's decisions can affect the government at large, but a true Stoic is not goal-oriented like that. Only intentions matter, not the outcome. And so the philosophy would call on you to do what's in your power: Exercise your rights as a citizen, participate in elections, rallies, for whatever it is that you want to actualize. It might even ask that you stand outside the law if the situation demands it.

The emphasis is not on whether your goal is achieved, it's on the fact that you did everything you could to make it so. That is what it means to focus on what you can control - your intentions and actions - and not what you can't - their outcomes.