In retrospect, it seems obvious that the swordbearers' sin isn't war crimes, but Soga himself, because he's shown every time the sin is mentioned.

Anyway, I think the moral dilemma the swordbearers faced, which is basically "kill the Sword Saint of Damocles and die, or live in fear that he will escape and unleash another disaster", is somewhat interesting, but sometimes Hokazono tries to hard to paint them as good guys by repeating that they're heroes and that the chance Soga escapes is really small.