The world doesn't need another political manifesto. And it seems you don't want to write one.
...not have the story devolve into a series of political debates or "get out the vote" rallies.
So, why not have a complete and total deux-ex-machina? Some magical character or magical artifact that causes the reversal of fortunes you seek to bring about?
For example, the Narnia series features a witch who sets herself up as queen and brings a century-long winter to the realm. This is brought to an end when a magical lion, and four children teleported into their universe from a magical closet, confront the queen's forces in battle (yes, some violence there). Make a non-violent version. In the previous volume, <PERSON> created the world by singing. Create a version where the <PERSON> stand-in character ends the winter and melts the queen's cold heart with song. (Is that the plot to Disney's Frozen?)
Also consider some magical artifacts. <PERSON> had a sword that only he could pull from the stone. He also had a magical scabbard that would prevent him from dying in battle, no matter how badly injured. Even more impressive the the Point of View Gun from the Hitchhiker's Guide to the Galaxy. Anybody fired at with this device is immediately able to consider the merits of another person's opinions, no matter how close-minded before. 805
Wow!
Another plot device you can use is dreams, or some other means of psychological epiphany (preferably unbidden and unwanted for the recipient, as dreams are). In Robinson Crusoe, the protagonist sees a deity eponymously named "<PERSON>" (after the author) in a frightening apparition in a dream. In the New Testament, it is said that <PERSON> was reluctant to crucify <PERSON> because his wife had a bad dream and warned him. This seems quite unlikely for a number of reasons, but it works in fiction.
Have somebody appear from our universe into the fictional world to intervene, like the kids in Narnia.
Maybe have the universe itself correct the situation. Signs and messages from the stars and planets, maybe messages from insects, talking animals, and sentient plants, a la the movie Avatar.
I've got it. Perhaps the head honcho has some illness or physical affliction, so he starts experimenting with smelling, or eating, a mysterious plant. This unknown, mysterious plant magically makes him calm, a little bit absent minded, and empathetic--and less prone towards violence and tyranny. He no longer forbids this plant to his subjects, and others start eating and smelling the plant as well. Meanwhile, the hardliners of the government are displeased. They try to enslave innocent young men to become goons for the war machine, but they escape to the Magical Wintery Kingdom of the North. At the same time, some strange messengers appear from a faraway land, and start talking about their dreams and singing songs about imagining things and foretelling the coming of a new age. The masses worship and honor the new messengers and their songs become known for generations.
That would make for some pretty interesting fiction, in my opinion. 322