Also perhaps worth reposting here:
My first reaction when the pieces fell in place was a resounding NOPE.
NOPE. *toss the computer out the window* NOOOOPE.
It can't be right. I reasoned. I know Solas. Falon'Din was a monster, the antithesis of what I believe... no, what I know he is. Solas is compassion. He is fairness. He is a stubborn, bull-headed champion of free will, tolerance, kindness, and faith in the human spirit. (ok, yes, "elven". You know what I mean.)
How can I possibly reconcile this with Falon'Din?!
There is a way. Let me explain. The Solas we know was not an illusion. He was not "faking it" with the Inquisitor, not presenting himself as fundamentally different from what he was. What we understand of his nature and his motivations were always, and continue to be, his true and honest beliefs.
The critical thing to remember is that it is his perspective, not ours, that shapes our understanding of Falon'Din's crimes. He is telling his own story, coloring the events with a degree of recrimination, guilt and self-loathing that is not, if were we to examine it objectively, necessarily deserved.
The "followers" that he describes in his story were not mindless worshipers. What he's actually describing was a social rebellion, a failed one that Falon'Din led and encouraged, which swept through the lands of Arlathan. In his telling he twists this into an act of pride, making the deaths of those who died a personal sacrifice to him- to ideals that he identifies so strongly with that he's blind to the fact that they were not for him. The elves who gave their lives in the attempt fought and died because they believed in the same ideals. They died for their own beliefs, not to vindicate his.
Solas thinks they died because he was too proud, too certain, that the world should change and that he could change it. This, I believe, the primal sin of Pride that haunts him. But it's not true.
"You didn't do it to be right. You did it to save them."
Cole can see it, even if Solas can't. He didn't lead the rebellion to be right. He did it because it was right. Ages of guilt and sorrow have blinded him to his own motivations.