I don't recall Hassildor being particularly anti-vampire. Sure, he sends you on an errand to kill some vampires, but not because they were vampires. It was because they were stupid. Because they are stupid, they're drawing the unwanted attention of vampire hunters and he is worried about being found out. So, he sends you to kill the vampires so that the vampire hunters will go away, keeping his secret safe.
True, but i remember his opinion towards Vampires in general being quite negative, i believe he said "
They have given in to their instincts, and are little more than animals. They need to be exterminated, one way or another."