Being a mortal could be regarded as a curse: Every other thing is immortall, and you one day die, and your very soul is played with and you can't do anything about it.
Being a vampire could be regarded as a gift: Immortality, and the power to give it to your loved ones, or cure them from diseases that could cause much suffering.
Dualities. Dualities everywhere. Are snakes evil? They are just doing what they were born to do. The best answer to every morality question like these is Balance.