How is Red Lyrium his MO? Fen'Harel seems far more subtle than that. He achieves his goals with lies and subterfuge, not with madness and corruption. If anything, this seems like a Forgotten Ones kind of MO.
We know almost nothing of the about the forgotten ones. and yes it is his M.O, pushing people to the extreme of there hatred. red lyrium isn't madness, its just the extreme of there character, bartrand became obsessed people would steal from him, while Meredith Became so disgusted and fearful of the Mage's. like i just spoke of yesterday. He makes some blind by there emotion that they dont see him coming, he did this with the creators and the Forgotten Ones, by making them so blind with what they wanted. the Creators wanted peace, and the Forgotten Ones wanted victory.
And we have heard him mess with emotions before making them to the extreme, or close to blind rage. We see that in the TME in the story about the tree, after he tell andaris he owes his victory to Fen'Harel. and that made him so angry that all he could do is yell at Fen'Harel so he didn't see Andrull coming up from behind him to mortally wound him. and then Fen'Harel got what he wanted. he was able to escape.
And don't you think all these conflicts seem like his action? Whispering to Loghain making him paranoid and Blind with anger, but once he lost to the warden he becomes completely reasonable and knows what he needs to do. I mean if you want to read more about my idea how the elder one is gently pushing people in the direction he wants. page 26 and 27 should have a discussion about it.
Edit:I will say, that madness is the incorrect word i should have used during that discussion, because i dont see red lyrium as madness. just pushes you to an extreme emotion. I apologize for that.