While I agree with most of what the posters before me said, I do believe that Alistair's reaction when thinking of recruiting Loghain might have been done better in that he might have been written so as to be able to be influenced in his decision based on the Warden's influence with him.
For me personally, the first time I tried to recruit Loghain my PC was romancing Alistair. What a blow it was for me to see that everything that had to do with his (understandable, but admittedly pretty borked) principles on the matter seemed suddenly so much more important than the months we had spent together and the relationship we had built up! Bluntly said, it felt like he was choosing Duncan over me, and that didn't sit well with me. :I
I don't need the option to have both of them in my group. What I would have liked to see, though, is a bit of a more gratifying outcome for people with high influence with him....... an outcome that wasn't quite as hostile.
If you're romancing him, it's even more of a betrayal to him. Pure and simple. He has more reason, then, to be hurt and angry, not less. He could equally say, that you were choosing to let Loghain live over him. Or choosing to believe Riordan (who you barely know) over the months you spent with him. I could not even conceive of betraying someone I loved that way, given the context (sans metaknowledge).
Because, same circumstances. Why would the HoF agree to it, after having gone through the same things with him? After seeing what Loghain put him through? Especially if she is a mage or Cousland? After everything Loghain did to her?
Geez, if you see him at the Temple, the man thinks he should have died instead. On top of everything else, he has survivor's guilt.
And it is also true that he is, at this age, an "emote first, think later" guy. No one's taught him any differently. He mourns immediately, and apologises later (although in this case, that's a strength, not a weakness: he was in a safe place, physically, to mourn, in any case. He thought himself alone, again--he was sure the PC was going to die, too. Better to get that over with straight away). He angers quickly (think of his reaction if you kill Connor or Isolde) and apologises when you point out that his motives for being angry are Not Just About Them. He's alone, all the time--and has been, all of his life. Discarded first by his father Maric, then by Eamon (don't even get me started on how effed up that relationship is), then by Cailan, then by Goldanna (who, btw, just happens to give him the new information that his "mother" died giving birth to him--oh, and that "your royal father forced himself on my mother", so he gets to hear he was a product of rape, who killed his mother. Not true, of course, but he doesn't know that--and even if he doesn't believe it: imagine being told that!).
All but Duncan. Who Loghain got killed. And maybe, against all else, The Warden. So, especially if you romance him, or are his bff, this is another "being discarded"--rightly or wrongly, that lizard brain of his is firing. He trusted you to do what you have both been talking about all year--justice on Loghain. And you betray that. Again, he gets to stand alone. And your PC puts him there.
Nope. Anything else than how he reacted would have been poor and contrived writing (that Riordan doesn't explain earlier--that's the poor and contrived bit).
I had 2 Wardens who did it. One despised Alistair. He was a human mage, romancing Morrigan (and a blood mage), who just got fed up with all of the "I don't wanna be Kings" and "blah blah blood magic bad boo" from Alistair so he did the absolutely worst thing he could think of to "get" to Alistair: first, he married Alistair to Anora, then he had Loghain join the Wardens, then did the ritual with Morrigan--and then disappeared 2 1/2 years later into the Eluvian with her, so "middle finger, Alistair". (My only other Warden who disliked him that much at least let Anora execute the boy. It was kinder).
The other Warden who grabbed Loghain did it because I wanted the achieve. She was a casteless rogue romancing Leliana and was fine with Ali, but read between Riordan's lines--she was used to the sort of doublespeak Riordan threw out so "got" something else was afoot. She put Anora on the throne (because she did like Ali she wasn't going to force him to take it), then told Anora to eff herself when she tried to execute him. She was genuinely surprised at Alistair's strong response, because that sort of crap goes on in Orzammar all the time: your enemy today may be your friend tomorrow, kinda thing. Swiiiings and roundabouts, etc. She then refused the ritual, and told Loghain to go kill himself, please, because she sure as the stone wasn't going to kill herself if Loghain was available to do it. Alistair became a drunk refugee who turned up in Kirkwall (and don't get me started on that... never mind.
)