Given the vampire's ability to talk to and usually have once been human it's cognitively much different than humans eating cows. To think otherwise is to diminish humans and to anthropomorphize cows.Not being a vegan or vegetarian, I'm looking it objectively.
First, animals do have feelings. Whether or not they can build a car or not, or write a novel or not is completely irrelevant. They feel sadness at a loss of a 'friend' or 'family member', at least what I have detected in domestic pets. This is probably the best way to describe how they are similarly.
Example is if a dog killed your favorite cat. Is the dog evil? You could think so, because that cat has meaning to 'you'. It's amazing how we are ok with a mountain lion killing a fawn, but if the same killed a child? It's a 'man killer(!!!)' and must be put down as dangerous (if not evil).
That isn't the case with the Vampire.
A Vampire kills just for the sheer joy of killing, of denying life, hope and future to those alive. They are in a state of stasis - hence all the things that weaken them - wooden (life) stake through the heart, running (flowing) water, holy symbols (afterlife). All those things have a tie in with life, hope or movement. A Vampire has none of these things - just envy and hatred for those who do.So a better comparison would be a person killing other people (and animals) because it can, because it wants to. An not just to "get by", in some cases Vampires will just be stuck with that for their own survival but that is not their ideal situation.
And the reason I say a person/human is because we need a self-aware component to the formula. I'm not downgrading animals here or saying they are without emotions or capable of feeling sadness - we just need an better example of something that is self-aware and has the capacity to know right from wrong.
Vampires want to kill and corrupt life because it's their desire to do so - because they are forever removed from life and even the prospects of an afterlife. The original myths were associated with plague, disease and fear of death (with some crossovers to fear of starvation/cannibalism). A vampire is those fears made manifested in (un)dead flesh and motivation.