Edelgard did nothing wrong and she is a good girl.
But seriously, History, as Mr. Williams, alluded to is filled with morally gray leaders; It's the fact that Edelgard is trying to change the world into one that is less dependent on the church, crests and status that I agree with her though I havent played the other houses yet, so maybe I'm terribly wrong or FE does one of those things that makes the enemies more evil than in their own campaign.