I am not arguing whether it was moral or not to kill Susan.
I am arguing that the ritual that Harry used was a evil ritual, as Morris said, regardless of how it was used.
I am arguing that using dark magic, even for a seemingly good result, still leaves a taint. A magic taint.
I am arguing that there are consequences beyond the Laws of Magic.
Mira, I would argue that while some men Fall from grace, some are pushed. Molly is in the latter category.
Arjan, we could have a debate about the ethics of whether killing a small nation of beings that murder, torture, terrify and feed of humanity. The problem with utilitarian ethics, is that it still sucks for the few it doesn't benefit. Which flies in the face of the Christian belief that EVERY soul is worth saving, every person's life is important. Which lines up with the Dresden Files - Harry started a war over one soul, one life (Susan) knowing that it would cause terrible destruction. You might argue his choice was foolish (although I suspect Mirror Mirror will answer that). You might argue that he didn't fully appreciate the consequences of his actions (as the White Council did). But the answer Jim leans into, if you read closely, is that it was the right decision and that war was always coming. There is a recurring theme that one soul is always worth saving and fighting for. But I will leave it at that.
G33k, you are essentially right. Harry practically committed war crimes (although you could argue that it is impossible against non-humans, as war crimes only apply to humans - but as Jim points out that is hardly fair).
Morris - you've hit the nail on the head. Agreed. And yes, parallels between the Fallen's treatment of Harry and Harry's treatment of Susan. I would go further and say Harry has been moulded for his whole life to do something just like that, even if it benefits the "good" guys. Harry is human enough, for the purposes of the book. He isn't totally (wizards are called freaks by the White Court) but he is mostly enough for the supernatural world. Only Jim knows where the line is. He certainly isn't by our standards, but as we don't have magic here (probably) there isn't much point in discussing it.
Avernite - you are insisting he didn't engage in black magic, but you're basing that on your own opinion. You have failed to provide any evidence that it wasn't black magic, other than assertions. Considering how little information on black magic we have, that is understandable. But you need to do better and find some references to what does or doesn't qualify to support your argument. As for the whole Archangel supporting his actions - 1) that's not been confirmed, but even if it was an archangel speaking through Murphy as others have pointed out that doesn't necessarily mean it was Right. Jim's whole point in the quote I provided is that Right and Wrong aren't necessarily owned or defined by the "good" or "bad" guys. A recurring motif is that there are lots of elements of grey (which even Harry isn't sure of) in morality. You might disagree, but that's how the books are written. I would also argue that just because the Almighty (TWG) thinks its okay to do mass destruction, genocide is genocide and many people might have a small issue with it. Including Dresden.
For those that argue that the half-vamps are not human enough, may I remind you that Thomas is mortal enough to be Winter Knight. Think less like the White Council and think more cosmically about Choice and things will get clearer.
Mira - I never said someone steps in front of the metaphorical car. Legally you'd still probably get a charge (although a number of factors such as what country you are in, how powerful your case is, your lawyers versus the families etc would affect that result and the severity of it). If you don't drive the car, no dead person. Harry doesn't use the ritual, no dead half-vamps. The ritual is black magic, built with black magic. Hell it is even built with a bloody dark ley line. Some of you need to re-read Changes.
CrusherJen - probably right about how much taint comes is partially to do with intention as much as result, and Susan's own Choice.
AClone - Have you read the Dresden Files?! The White Council exist in the story mostly to make Harry's life harder! If they can prosecute him for something, they probably will. It's all they do for most of the series. Just because Harry helped with one problem (which created arguably a greater problem) doesn't mean he'll get any thanks. Which is essentially the feel of Peace Talks anyway, more of Harry's choices coming back to haunt him.