Not only that, but we see that there are vampires who can control the elements. We know that Neferet can erase minds. So the Cast ladies can tell us that the humans are stupid and irrational for distrusting vampires all they want. The fact remains that vampires CAN do all sorts of nasty things to people and don't feel fit to warn the humans about anything. Hell, they clearly weren't bothered to tell Heath's parents what happened to him.