Ah. Looks like that one scene in TDKR where The Joker Jokers everyone in the audience.

This is somewhat related to a plot device in a story I'm writing.

In my stories, vampires have always existed and require the consumption of blood from others to supplement a fictional cell that they cannot natively produce as part of a hereditary curse put on them for the sins of their past ancestors. Human blood contains a good abundance of these cells, but so does animal blood, albiet at a lower quantity and with a disgusting taste. Pacifist vampires willingly stick to animal blood in an attempt to live peaceful lives, but humans will irrationally attack them if they're exposed for being vampires. Purist vampires see humans as inferior beings in every way imaginable and see no reason to take animal blood when humans should be serving then, so they wage war on hunanity every once in a while, but a weakness to sun and silver keeps them in check.

In the present, a cryptobiologist manages to synthesize this cell after freeing a couple of pacifist vampires that the purists were keeping as slaves, but the purists find out about it and go after the biologist for, basically, threatening their image of superiority, but this is in modern times and they terrorize him into patenting the synthesis process and handing it over to them, akin to what they did with insulin IRL, but they have no intention of ever making more of it.

The war against vampires never stopped. It just changed.