@Z Sure, she was more moderate. They both were, before the idol showed up.
I don't think she had any higher ground in the end. And she's an adult, remember? One person pushed to do the RoA after she went mad and she just went with it? That's what a child does, or someone that's gone mad. Yes, she was being childish by calling the RoA, and in the wrong too.
I'm sorry, but that sounds like something my pre-school nephews would have as an excuse, "But Mom, he made me do it!"
Also, Anders had mentioned in earlier acts that Meredith wasn't that bad. Neither was he, remember? He was healing the sick for free, running a mage underground and trying to spread the word about some of the treatment of mages in the Gallows. It was confirmed by at least one member of the Gallows Circle that physical and sexual abuse had been going on.
You say that Meredith's deteriorating condition was due to the idol. Anders was due to Justice. Both of them were having their sanity slip due to magical influence. You're trying to tell me there is a difference between the two. There really isn't, not by the end of the game.
I hope I've made it clear that I think both of them had a point and both of them did a very bad job of conveying that point. That's why I'm in the middle. To me, the decline of both Meredith and Anders is comparable, and shows why such extreme examples of Templars and Mages have hurt the narrative.