However, in recent years, we have seen movies such as Underworld, where the vampires ostensibly did not consume human blood. The vampires in the movie Underworld were a pretty rotten bunch and it would be hard to make a case they weren't evil. For some time, vampires have been able to obtain human blood from blood banks. Ergo, no need bite someone in the neck, lethal or otherwise.
So, if a young woman or man, living a virtually "pure" life, was turned into a vampire at the present time, there would be no need for this person to take blood from a mortal. Clearly, if a vampire kills, then the vampire is evil. However, this would be true of a mortal who commit murders. Without committing any acts that harm a mortal person, it seems to me that the vampire cannot necessarily be considered evil by solely by being one of the undead.
I'm sure that many people would tell me that I have oversimplified the issue or question. If I have, then I would like to hear the "complete" explanation of why a vampire would necessarily be considered evil.