What I've always found fascinating and horrifying about Justice possessing Anders is that, while he's still devoted to Justice, it's become focused only on Mage Rebellion. Everyone and everything that stands in its way is an opponent against Justice, and should be righteously terminated.
Anders is the only companion to approve of Fenris being sold back into slavery to Danarius, because Fenris opposes the cause. Justice creating a black-and-white dichotomy is the only way I can justify (hehe) that.
Likewise, Elthina and all of the people, whether it be priests or people there for help and sanctuary, are tools whose use for the cause is to burn.
I mean, I'm not fond of Elthina, personally. I can see why she would try to remain a neutral, stabilizing force, but it drives me nuts that the one force both Orsino and Meredith respected did not take a more proactive stance in shutting down the rampant blood mages and horrific abuses of power in the Circle.
I think having a sword and Tranquil brand above their heads legally, and rape and post-Harrowing Tranquil brand above them illegally, has some damaging effects on mage psyche. The constant abuses alluded to in DA2 make Greagoir's stern oversight in Origins seem fair, but even then, you've got Irving's determined politicking to strike a blow against the Chantry for every mage of his lost, to make sure they don't get too upity.
I'd be an Aequitarian myself. The mages managed to get themselves out of candle-duty and into Circles back during the early days of the Chantry. They should be able to curtail the Templars' abuses without starting a world war. Then again, they proved themselves hopelessly incompetent in Inquisition, which is to be expected since they've never had to handle independence or political power like that before.
...Though you'd think they'd recognize Tevinter as a bad ally.
Rhoxi: Yeah, apostates don't really get to solve the Circle problem without violence. 
It's why I suspect most of the Libertarians are really in the Aequitarian or even Loyalist factions. Only the really hardcore, passionate ones are silly enough to paint a target on their head for the Chantry and Templars, while the wily ones would quietly increase freedoms in one of the 'stable' groups, waiting for the opportunity for a big push. I haven't read Asunder yet, how do the Fraternities interact there? 
I'd try to go for political reforms by using the political sway mages have. Mages are essential to any kingdom's army, the Grey Wardens, and serve in courts as arcane advisers. That's influence. While the Templars could annul them for trying to get more rights, the Chantry at large would take notice, as would the other Circles. That kind of attitude wouldn't work out. (As Meredith proved so well.)
I definitely understand why Anders would lash out, because you can only handle so much patience and careful maneuvering when the other side routinely rips away your friends' identity. Especially when they then proceed to use the punished Tranquil as one of their main sources of income, which is one of the shadiest things in all of Dragon Age.