When I see moments like this, I’m reminded of how important it is to remember the context of DA2, which is that this is a story that Varric is telling a hostile audience (hostile in more ways than one). And it would have been so easy -- and smart -- and sane -- for Varric to deflect all the blame for what happened onto Anders and Anders alone, especially if he wanted to protect his friend.
But instead Varric takes pains to make Anders sympathetic and his cause righteous. He takes so many pains that in many ways it becomes dangerous, even subversive.
I mean, think about this scene, where Anders is telling Hawke about his many escape attempts from Kinloch Hold. But layered on top of that we have Varric telling Cassandra this story, right? So, essentially, Varric is saying to Cassandra that the embodiment of Justice himself was so enraged by the idea of the Chantry locking up mages that he literally could not stay silent a single second longer in this conversation; he could not control his rage, he had to let his voice be heard. Varric is saying that denying a mage seeking his freedom is, fundamentally, an unjust thing to do, because Justice himself condemns it. And Varric is saying this to a Chantry Seeker, whose very job is to support the Chantry line, which is that mages are dangerous and must be locked up for everyone’s protection. And if you think about how much of a fuck-you all this is, well, it’s a wonder Cassandra didn’t stab Varric right through the book again.
Varric never publicly picks a side in the mage-Templar war -- as he says in game, he has apostate friends and drinking buddies in the Templars -- but if you sit down to really parse how he tells Hawke’s story to Cassandra, especially what scenes and conversations he chooses to include, I think the side Varric falls on is very, very clear.