Just because it's your job doesn't mean you chose it. [Shun's well aware that many of the people he's at war with were indoctrinated into their ideas of battle, and he's met one or two who he would have felled just the same if they hadn't had the chance to break out of that mindset before he needed to. A "job" just means something someone else is having them do.]

Even if you've been doing it for a while, when you were given more options here, you chose something else for yourself. I think that speaks for something.

[It sounds like she's trying to remove any justifications for it, in which case Shun is just going to point out that it's not really any more or less forgivable as the kinds of things plenty of other people here have done.]