So, I had already finished the entire questline for the Vampires and got my Vampirism cured, then at one point I eventually decided to join the Companions to become a Werewolf, after becoming a Werewolf I was still being attacked by the Dawnguard. Now I don't know for sure if this is due to me aiding the Vampires, but I feel like its a bug in the game where the game itself "forgets" to disable the attacks since I'm no longer a Vampire. I could be entirely wrong on both fronts but I gotta be sure.