Do they say "justified"? I thought it was more along the lines of "this isn't an unreasonable thing for a human being to do." She doesn't want to support Loghain. She's perfectly willing to work with the Warden to remove him from authority. She just doesn't want him dead.
I'm still not getting why Alistair, who also risks the Wardens' ability to defeat the Archdemon - and not even for a person, but for an idealized conception of an organization - is the better pick based on this criterion. He doesn't even think what he's doing is best for Ferelden; he just plain doesn't like it and won't stand for it.
1) There's a few of objective flaws concerning the "Recruit Loghain as a warden" situation that honestly come down to plot contrivance. There is nothing to suggest that Loghain is the only viable option as a warden in that situation especially when the wardens can easily recruit more wardens from their companions or from the many factions currently under the warden's command. Recruiting Loghain just for the sake of getting more wardens false flat when in a none-contrived situation, he wouldn't be the only possibility.
2) Loghain has just spent the past year hunting down wardens and driving Ferelden into the gutter. Any merit that he may have as a potential warden is muddled by everything that's he's done and how it's only made the situation worst. He's not only untrustworthy, but he's clearly shown himself capable of letting his personal bias and feelings obscure his judgement which nearly led to his nation's destruction.
3) I'm assuming that you mean Hardened Alistair who marries Anora because Unhardened/Hardened Alistair will be executed or driven into exile otherwise. Hardened Alistair doesn't initially want to be king, true. But he actually thinks it over and decides that he does want to be king and believes to be a good leader and as the epilogue shows, he's willing to learn everything that he needs to become a fair, firm yet beloved and effective king of Ferelden. The very notion that he doesn't want to be king at first shows that he's got a good heart and that he decides to be king for Ferelden's sake rather than his own is also another good sign. It shows that Alistair can and will do what he must for Ferelden's good.
Then there's how he's risked his life for the past year against darkspawn, demons, and etc. to save his country at his own volition. He'll even stay to fight even if he hates the Warden and their decisions.
4) As for being mad about Loghain being recruited enough to leave the party, it is identifiable, but still selfish of him, I'm not going to lie. I'm not sure if he outright deserted Denerem or the army though since he shows up at the celebration after the battle is over. It's very possible that he was still fighting in Denerem, but simply refused to serve alongside Loghain. Considering all of the #$%# that Loghain has done in the past year and how it's all affected Alistair on a personal level in many areas (Eamon and his family, Duncan and the Wardens, Cailan, Being on the run for a year, Ferelden about to be handed to the darkspawn because of Loghain's paranoia over Orlais), I wouldn't blame him.
Especially considering the context, Loghain has just been found guilty before all of Ferelden of his crimes and Riorden suggests making him a Warden just to fill a quota. Alistair considers being a Grey Warden an honor, not a way to escape justice for clear treasonous and illegal activity and even the Right of Conscription isn't used quite so liberally (Duncan was guilty of second degree murder while the City Elf and Dwarf Commoner were honestly justified events of self-defense where they would've been punished wrongly because their societies are prejudiced and bias towards elves and casteless).
So let's see:
Hardened Alistair's qualities: Humility, Determination, Knowledgeable, Apparent Artistic Interest, Tolerance, Loyalty, Care for Justice, Honesty, Healthy self-Confidence and Assertiveness Putting Ferelden above himself as king and as a warden, Wiser than most see (Anora herself will admit as much) acknowledged as Kadan by Aristen (Arishok Sten)
Vices: His Tolerance only goes so far, Blunt about personal grievances, somewhat Naive, Incapable of working alongside personal enemies, Can be too emotional at times (Duncan and Connor).
Anora's Qualities: Ran adminstrative aspects of Cailan's throne, experienced, Intelligent and Capable, Direct though not overbearing, Assertive, Can be persuaded to share power (w/M!Cousland or Alistair), Natural Charisma, Cares for Ferelden.
Vices: Wants to protect her father from any justice he deserves, Will betray allies on a drop of a coin if it serves her interests, possibly Power Hungry, Holds an uneven opinion of her own capabilities in light of her powerlessness/inaction during the Civil War and the Blight, Her own loyalty is to herself, Is her father's daughter.
So there, Hardened Alistair+Anora is possibly the best outcome for the Landsmeet with Hardened Alistair's career as a good king being supported by in-game proof and the epilogue. Solo Anora? Nothing in-game suggests that this is exactly as good of an idea as Anora claims.