I don't know if it's the best choice, but Les Misérables springs to mind. I think the book in particular captures so well that inner turmoil of an impossible choice, but realisation that the selfless act is the most necessary one. I'm not religious, but I think if more people acted like the Bishop or Jean Valjean (especially those people who claim to be Christian but hold no Christian values) the world would be a better place. And it shows how just because an authority is the one holding power, it doesn't necessarily make it correct in its decisions.