I don't care about justice, I care about winning the war. Justice is subjective based upon the laws of the land. Loghain's (1) Turned much of the Bannorn against him and (2) Turned the Wardens against him, and both parties are required to win the war. If not for his actions, things would be better off. Getting rid of him gets rid of a lot of political complications and headache.
Technically he's only the regent, but in a Medieval state, from where do you draw your authority to rule? Military power. Anora has none. Loghain has all of it. He wants to rule Ferelden and for all intents and purposes, he does rule Ferelden. And he's not doing a particularly good job by causing a civil war in the middle of a Blight. That one is on him. What's to say that when the Blight is over, if he's spared, that he wouldn't turn on the Wardens again and try to seize power a second time? We don't have any hindsight in the first game, so there's not much to go on. He's no less a pretender than Alistair is, but at least Alistair's not constantly trying to cause problems.
I absolutely would prefer Alistair be king. His chivalry and selflessness may not make him a perfect king, but I doubt he'd be as keen to spill blood as Loghain. He also doesn't share his bed with someone like Arl Howe.
If you cared about winning the war, you would use every resource at your disposal. You do not. So I am not convinced.
Canon and political cunning disagree. Keeping him alive, esp. with Queen Anora in power (Married to Alistair or not) and the Warden as Chancellor creates poltical stability. The Bannorn continue to cause trouble whether he lives or dies. They would have rebelled either way.
Ferelden is not a European medieval kingdom. In Ferelden the Landsmeet empowers you to rule and the Landsmeet confirmed Anora as queen who appointed her father as regent. Easy as.
He is a terrible politician. But he did not cause that civil war. The Bannorn did. And they continue to be trouble even if he dies. The Bannorn would have rebelled either way. (Ever wonder why Teagan was not at Ostagar........)
Canon and logic both clearly state that he would not. And he does not. So OOC conspiracy theories will not convince me.
We may not have hindsight but we have common sense. (Or so you might hope)
He is not a pretender at all. He is the appointed regent of the lawful queen. Like he was in King Maric's time. Alistair is the illegitimate pretender who needs a coup d'etat, treason and murder to gain the throne. AND he will only not cause trouble as long as he gets what he wants. If he doesn't, he selfishly deserts Ferelden and all of Thedas in the jaws of the Archdemon because he didn't get his bloodlust sated. But that's A OKAY because poor bby blabla.
Said "Selflessness" (Which he doesn't have) and chivalry make him a horrible king. As DAI and DAII confirmed.
Funny story, given that he puts his blood lust above his duty as a Warden. And that Loghain is not very keen on killing.
He just dogs a long behind a Warden willing to commit a coup d'etat and mass murder (Haven)........look, I'm no fan of Howe's. But I attribute Howe's failings where they belong. To Howe.