Even if that were true (the original vampires in Dracula may be soulless monsters who exist solely to kill, but that's not the case in most modern portrayals of vampires), I still think that doesn't make them any more dangerous and despicable than the Joker, Black Mask, Bullseye, and many other human villains.
For the record, I'm all for killing them all (starting from Bullseye). It's just the double standard that pisses me off.