If you read Morgana and Kayle's Lore, you question yourself: who is actually the bad guy here? As much as Kayle preaches about justice, it is actually "her own brand of justice". Kayle thinks of herself as the police, the judge and the executioner; someone who will make the rules and will make sure they are followed, or else you are destroyed. Aether Wing Kayle, a skin set in a hypotetical scenario in which she wins the war, has dialogues which perfectly depitc this.
Morgana, on the other hand, as evil and rage flueled as she is/seems to be, could very well have a point in her speech. No one really knows what she had to go through during the war, what drove her to master the black arts, and what sacrifices she made in the process. She is either a tragic heroine, or a great liar. She might be the one preventing Kayle from enslaving al of Valoran to serve to her kind, or merely wishes to enslave Valoran herself, for her own purposes. It's clear she stands against the angels tyranny, but there is no mention of what she wants to do if she ever wins the war.
In any case, after what I saw previously done to Viktor, another tragic character who was portrayed as a crappy villain from a 70's superhero cartoon in order to make Jayce look cool, or what is about to happen to Xerath, I fear that you might brand them by their appearance and portray Kayle as the rightful and Morgana as her evil counterpart. Neither of the two is free of sin, and I'd like it to remain like that instead of the usual oversimplification for clarity purposes.
I think the Angel's war, and the characters of Kayle and (particulary) Morgana have a lot to offer lore-wise if the morality of both sides remains as gray as it is right now.