Ah an interesting question. One I haven't had to think about in awhile actually.
My answer is: Probably, but none of my Hawkes kill Anders.
In Thedas, one person killing another is very common. One person killing a lot of other people is also common. Granted my Warden, Hawke and Inquisitor all only fought in self defence but they made certain choices with a morality adjusted to Thedas rather than modern day Earth.
My female city elf Tabris recruited Sten, a Qunari warrior who killed an entire innocent family of farmers for no good reason. She recruited Zevran, an elf assassin who has undoubtably killed dozens of innocent people. And she recruited Oghren, a dwarven warrior who was almost exiled from his people for killing someone in a "first blood drawn" match. And that's just for starters. There are all kinds of questionable decisions and quests Tabris could undertake. In Awakening she recruited Velanna who has murdered whole caravans of innocent human traders. She even recruited Loghain and fed him to the Archdemon.
Heh as a player I haven't even gotten on to DA2 yet and my hands aren't clean as far as allowing companions to live and/or recruiting them to serve with character.
My female apostate Hawke recruited Isabela. She's a raider and pirate. Undoubtedly she's a criminal and has killed people during her career. Innocent seafaring merchants perhaps? Either way she's hardly a good person. She also recruited Merril who openly consorts with demons and uses blood magic. Yeah Anders is possessed by Justice/Vengeance but at least he's not a demon.
And then there is Fenris and what he did to Hadriana. Granted she was a 'bad guy' and had done terrible things to him as well as just tried to fight us but she had been defeated and had surrendered. Parley and all that. She made a deal for her life and Fenris agreed-then proceeded to break his word and murder her. So now he's a killer too.
There's plenty more that I could say, especially if I added examples of mass murdering companions or choices in DAI too but I think I've made my point.
So as the player, yes Anders did a terrible thing and killed some innocent people but I've forgiven and recruited companions that are just as bad or worse than he is. Is he supposed to be different because we watched him blow up the Chantry while everyone else's killings took place off-screen? I don't know, it just feels a bit hypocritical of me to go around condemning and killing Anders for that given I've spared mass murderers, pirates and assassins before.
As for Hawke I apply similar logic. She recruited Isabela and Fenris. Her own body count is impressively high and she's done her own questionable things throughout her stay in Kirkwall. It seems a bit hypocritical to kill Anders at that point. Plus she's a mage herself and sort of sympathizes a bit since there's no question that the mages are being horribly abused in the Circles-especially Kirkwall's. Seven years of Anders trying peacefully has gotten nowhere. Neither Elthina nor the Chantry are going to change peacefully.
So, my Hawke both spared Anders and took him with her to help atone for his crimes by helping defend the Circle. In my mundane Hawke playthroughs since I never brought Bethany to the Deep Roads she's currently trapped in the Circle that Meredith intends to annul. So she sides with the mages. Its a bit hypocritical of her to kill Anders, she has to save her sister. Meredith's call for annulment is illegal. Anders is the team's only competent healer so she also spares and takes him with her.
Both my Wardens and Hawkes believe in atonement. Loghain atoned with his death. Perhaps Anders doesn't need to die to atone for his crime.