Evil and good people are present in all races, most Vampires if they aren't starved because of hunters chasing them off nonstop, they will just feed and move on.
Doing what you have to do to survive and not go insane isn't evil in my opinion.
That is like saying just because a redguard bandit kills a innocent noble, that the whole Redguard race must be evil.
But they DON'T have to... as others have said, they can be cured.
Even if they only want vampirism for immortality or a power trip, they can't be trusted with that power. As I've said, if a vampire could prove that they were not a threat to innocent people, let 'em be (but they CAN'T prove something like that). Otherwise, that power that you've chosen or been bestowed is too great. Cure or die.
EDIT: If you're looking at this from a completely relativistic stance, then you can say pretty much anything about anything. That renders discussions boring. If you want to cut that fat, and be a bit more utilitarian, we can evaluate this from the perspective of the greatest good for the greatest number of people.
Being killed/preyed upon is bad. There are more non vamps than vamps. Not all vamps chose to become, but that's irrelevant since they can be cured. They can't prove they aren't a threat to innocent folk. That power puts them at a great advantage over most mortals. They must prove they aren't a threat (again, don't know how), be cured, or die. These are the only three routes to removing that threat. Pick one.