Also, OPOI, so random vampires who have showed nothing but ill-intent are now more deserving of life than innocent childhood friends who have been abused for eleven years? Your Shirou is a dick....
Hmmm...was I too quick with character development? My bad, I'll be more ruthless next time
Well, it seems a bit odd that, after coming to the conclusion that he had to murder the girl he loved in cold blood to prevent the
possibility of her hurting people, and showing the willingness to murder another girl in cold blood on the off-chance that Forest and Rider might fight over her, a couple of words from a girl he only just met would cause him to spare someone who, frankly, he probably
should have killed.
Whilst I could
perhaps see MoS Shirou coming to recognise that what he did to Sakura was wrong and that he shouldn't kill people without very good reason, I don't think it would happen that quickly or without any mental repercussions. If he's willing to let a vampire like that go, then he should be completely tearing himself apart over what he did to Sakura, since he now cannot in any way excuse it. If a
vampire (i.e. someone who feeds on people) who specifically showed up to attack him and who seems to have ill-intent is spareable, then there is no
way he can justify killing Sakura on the basis of what he knew.