I don't like the vampire attacks because they stop once you finish the Dawnguard DLC. This pressures players to play the DLC even if they want to save it until later.
Sadly you, like myself, seem to be in the minority.
There are plenty of people like carrots going on about "THESE ATTACKS GIVE A NEEDED SENSE OF URGENCY TO COMPLETE THE DAWNGUARD QUEST!!!" when there is absolutely NO need at all for this "sense of urgency", and it is the exact opposite of what Bethesda has markteted Skyrim and the TES series as.
Regardless of Faction choice, the Vampires are always hostile. They're rogue Vampires, not Volkihar-descent.
After completing the last Dawnguard quest, the attacks will stop.
I could go into further explanation as to why it would end if you choose the Volkihar... but that would spoil it and I don't think you've gotten that far.
There is also the BUG where they still attack even after you beat the main quest. Combined with the BUG where you get attacks every single time you attempt to get near to civilization, it becomes rather frusterating...