Pretty much the idea I had in mind when I chose my user name here, in a flurry of youthful indiscretion.
Anyway, all it would require in-game is a sense of hopelessness for the people and a sort of cultural permission.
Imagine a world where there's still a clan of dwarves under servitude to giants, who have tried and failed numerous rebellions, who can't get outside help (maybe the giants have powerful allies), who grow up knowing only that they are fit to work for and be murdered for the glory and joy of the Giants, who know that they cannot act to influence the world...
...and then one hero steals fire from the gods, straps it to his back, and manages to give them a glorious, flaming hope. The temple of the Giant's God collapsed. The hero died (as all good heroes do), and the giants rebuilt (as all good villains do), but there's still a hope there. A sign, for the religious-minded dwarves. A reason to die for a cause you believe in, when your lives are chained to causes that you cannot have faith in, for the suffering you and your loved ones endure for them.
Now, it might not be logical, or effective. It might ultimately be self-defeating. But your life is hopeless, you have no escape, your family and friends and loved ones and children will all suffer as you have, or worse, and at least in the Halls of Moradin, you will be greeted as an agent of change and revolution, having struck a blow against the tyranny of the giants.
The worst that could happen if you decided on this course is that you go out in a blaze of glory trying to give your people hope. The best that could happen is actually the same thing.
The greybeards who speak of the futility of the action keep trying failed policies. Their age has made them impotent, their experience makes them afraid of death, they want to live for their families. You, as a young dwarf, have no such responsibility, no such connection. You have your justifiable fury, and access to cheap gunpowder.
Now imagine playing a character who was one such dwarf....but who lost courage at the last moment, and ran away, and managed to escape the Giant Lands, into a region where they did not dominate.
Imagine the guilt that dwarf feels leaving his family there, in the clasp of the giants. Imagine the certainty he feels of his damnation -- he won't be welcomed into Moradin's Hall as a coward, as a turncoat, as someone who refused to strike against the Giants when given the opportunity...
...imagine the sort of Epic-level quest that it would be, toppling this ancient giant empire, and liberating the dwarves, and giving them a hope they don't have to die for.
...of course, I do like a game with moral ambiguity in it.
