Nobody chooses to be a vampire. It's not a life choice, it's something that you can't help. It's not fun and shits and giggles, you know. Nobody wants this.

They were human once. They can still think and feel - Trust me, I work with the undead, this is how I know, and my ethical standards say I don't use my magic on a sentient, free thinking member of the undead. Which, undoubtedly, every single vampire on board is. So it's torture.