I joined volhikar and become a vampire.
Yes. I am their enemy.
But what actually triggers them to hate me?
Is this because I am a 4th stage vampire? Does that mean if I drink blood I can come to Dawnguard fort and buy spells?
Is this because they know that the dragon born is an evil vampire that will kill them. Then why don't they tell everyone.
I am at destroy Dawnguard quest.
All guides say that I should cast harmony if I want to buy spells from them. Why?
Update: 4th stage vampire is NOT the problem. I feed on people. I talked with normal people normally. Yet dawnguard girls still hate me.
The most likely answer is that dawnguard can know my faction. However, this is very unusual. I joined stormcloack faction. I can go to imperial camps and they do NOT attack me on sight.