Yup, but the majority of them of them are evil bastards who just cause trouble. Can't expect the Dawnguard to know, or care about the minority that "aren't that bad".
They gotta focus on the majority that's kind of.. Invading towns, turning, and torturing people.
And what about the majority of the Dawnguard, invading caves, burning and torturing vampires. If you kill 100 people and just one of them was innocent then you have comited an evil. It does not matter if they dont know, ignorance is not an excuse for murder, especially when fueled by prejudice
lol Vamps are people too