Vampires are a well established fiction (Vampires in literature became popular in the 18th century) and in most parts of history the majority of people believed in myths and the existence of mythical creatures. After all the last burning of a "witch" in Europe happened in June 1782. So "magic" and myths aren't as much of a problem as women with a brazilian wax look in a game with a ~17th or 18th century Transylvanian setting.
For people with knowledge this is comparable to some npc appearing in a spacesuit in that tavern. You just lack the knowledge, but still want to smart-ass as most morons do.
But I guess, that's way too much information for the majority of simpletons prefering only 2 lines of text drawing wrong conclusions.