If vampires existed, their diet would be more moral than that of humans.

Think about it for a moment: humans have concentration camps where we imprison animals, force them to reproduce, kill them, and all to eat them. And that's not even mentioning the environmental impact of factory farms, which is enormous. Even vegan food factories create a significant environmental impact. But on the other hand, vampires would simply kill someone random. There's no torture and no environmental impact. However you look at it, that kind of diet is much more ethical.