What I saw was a grown up man that couldn't accept the fact he wasn't gonna see Loghain's head on a spike. He was willing to abandon Ferelden and the Grey Wardens, just because he didn't get his way.
He was acting like an immature brat. I can tell you that Duncan was roliing over in his grave.
To you perhaps, what i saw was a man who was looking to get justice for his father(duncan was like one). There is NOTHING wrong in it. Infact ot was the right thing to do.
If you didnt notice that....what you refer to as immature man was supporting you heart and soul. Unlike wynne and leliana, he does not attack you if you defile the ashes, despite his indoc. in the chantry. If you didnt notice Loghain was trying to kill you the whole game. But ofcourse ppl like traitorous mass killers, not loyal frnds nowadays.