Congratulations. You have just accused everyone in the real; world of the exact same thing.
Comments like this sicken me. That's like saying citizens of nations under a dictator are responsible for the atrocities of said dictators.
Oh god. If I laugh any harder I'll throw up.
POINT THE FIRST: Chantry sisters are in no way living under a dictatorship. You seem to have confused them with the real victims, ie, mages.
POINT THE SECOND: People can't help being born into fascist countries, and they rarely, if ever, have the power to leave by legitimate means. By contrast, becoming a member of the Chantry's clergy is totally optional and you can quit whenever you damn well please. Sebastian quits and re-enters the order multiple times.
POINT THE THIRD: Not only do Chantry sisters not suffer. They explicitly benefit from being members of the Chantry. By rising through its ranks, they can obtain power that would otherwise be unavailable to them in any other faction. There is literally no other organisation in all of Thedas that works this way for anybody.
So, your hypothetical Sister Stacey can go suck a hypothetical lemon.