After watching the Dracula ballet last night, I got to thinking: if someone got turned into a vampire, is it best for them to be killed or not? On the one hand, we would think of them as a moral abomination now. We think that if we ever reached that point, we would want somebody to off us. So too should we kill the new vampire, for their own sake.
But on the other hand, they are no longer human. The standards for human flourishing (which, although this is controversial, would probably include not killing off friends and family to feed your lusts) are not the standards for vampire flourishing. A human-turned-vampire would be like a rabbit-turned-lion. You may be surprised at what happened, but you should not feed this new being hay if you want it to be happy (and I would prefer happy lions around, if I had to have any at all). This new vampire then should also be judged according to vampire standards. The human would not have liked this new life, but that is irrelevant to whether it is best for the vampire to live.
This then gets at one moral dilemma, similar to if a young person makes a promise that she later regrets when older - "whose" moral standard becomes relevant in deciding whether she should be held to that promise? What about if I say that I would rather be euthanized than be a vegetable in a hospital bed?
Of course, even if it is worse for the vampire, we could still just stake the sucker for our own sakes. We don't want creepy supernatural predators preying off of us, as human beings. So we can fight for the human good, against a world that sometimes just doesn't care about us.
But, at the same time, part of being human is that we can transcend our own local interests for other things in the world. We can identify ourselves with causes that may have no direct human benefit. (The one point on which radical deep ecologists and conservative Calvinists can come together?) So simply doing something because it is a human good is not necessarily the same as doing something just because it is good overall. And we as humans can think about this distinction. So then should we let vampires live out of respect for life (er, un-life) as long as they don't prey on us too much?
This dilemma comes up too in both the Greek and Chinese traditions (and I'm sure many others). We have the debates between the philosophers and rhetoricians in Greece and Rome, where the rhetoricians and sophists favored a purely human-centered life concerned with building human communities. Search for "truth" is secondary to these matters of practice. The philosophers favored finding what is true, even if it goes completely against what people around them took to be good. And part of this could even be for the sake of humans: current values concerning what is "good" can be revised. The Daoists and the Confucians have had similar struggles, with the Daoists focused on the Way of Heaven even when it completely called into question all typical human values while the Confucians focused more on starting with human beings and only dealing with what is relevant to them. Of course, this was not always a pitched battle; sometimes the two sides in both traditions have complemented each other, since human beings are not actually separate from the world in which they live - another tricky ethical point to work through.