I agree with all the Pro Serana people. If a certain country attacked my homeland, i wouldn't just go killing off everyone from that country just because they are from there, now would i? Substitute vampire instead of country. "Just because my home ( Vos ) was attacked and burned down by a certain order of vampires doesn't mean i go kill all vampires saying "Where is she!!!" The DG DLC gives you insight into how vampires aren't just these murdering, ravenous monsters that they are portrayed as. Serana didn't even get a choice to become one, and the process of becoming one was very traumatic if anything you should be feeling sympathy. That isn't exactly fair to compare too. Paarthurnax committed War crimes personally, that is part of the reason Delphine and Esbern want him dead ( besides there hate for all dragons ) so that is a pretty legitimate reason.