The members of the Chantry aren't as innocent as you seem to think they are. And how could the Mage/Templar war be avoided? It was only a matter of time before that situation would break out. The Chantry was doing literally NOTHING to help ensure peace between the two opposing sides. So how else was this going to be prevented? The mages were being oppressed and wanted/needed change. Anders blowing up the chantry only brought about an inevitable war sooner rather than a little later.
Also, I can't help but laugh at how people exaggerate the death count at the Chantry. It wasn't as high as many seem to think it was. There wasn't any service going on at the time and highly doubt the building was jam packed with people. The only ones we saw bite the dust were Elthina and like four or five Templars. And really, they kind of deserved it.
Do I support Anders in his decision to blow the place up? No. But lets not kid ourselves. Sebastian invading Kirkwall is far worse than the Chantry blowing up. In my DAII file, he flat out told me he was coming back to **** **** up. And guess what? Anders isn't even in Kirkwall. Sebastian is more insane than Anders is.
Really, so where the members of the Chantry out killing people? Summoning daemons? They aren't guilty just because they are part of the Chantry, it's not evil you know.
The Chantry was doing a lot to ensure peace, the Divine in the Capital (the world is bigger then one city) was working to reverse tranquility and was sympathetic to giving mages more freedom. How could it have been prevented? Peaceful talk and compromise, with a sympathetic Divine it would be much better then holding gun to peoples heads. Meridith was annoying a lot of people in power in Kirkwall by her actions, if Anders had killed her or just waited till she went over the line and is removed. People would have been a lot more sympathetic to giving mages more freedom. As it stands Mages are seen as the aggressors, and people are FAR less likely to have any sympathy for there cry of "Oh woe is me for I had to live in a tower and be given all my meals and cloths for my entire life", someone who just saw them blow up a building and now has no food, might just tell them to gtfo.
Also how do we KNOW it was empty? we only see one shot of the central Cathedral, in the medieval times churches often were also where the clergy lived and I think Seb lived in the Chantry will in Kirkwall, so there could be more people then you think.
Is the invasion of 1 city worse than a attack that is intended to start a war? I think that is debatable. (and look it is lol)
I would also point out I don't support the invasion, I feel if he went in peacefully and offered help (food) and leadership he would go better. In fact if Anders is dead doesn't he do something similar? I thought I saw that in a thread.
It just seemed really weird to me that people are all like "I hate Seb, wish I had killed him rrrhate", but Anders is fine.