Monster movies are going to be so weird in the future.... The threshold of disbelief won't be any higher, but it will have odd angles.
All the characters that don't believe in the (werewolf, vampire, mummy, alien, telemarketer, serial killer, giant alien zombie were-spiders) until they're attacked, THEN accept the reality, though usually fatally tardy? Gone, the same way, and to the same place, as the phrase 'avoid it like the plague.' 'Cuz humans don't do that.
Now, it won't be realistic unless the victim refuses to convert even on direct eyewitness evidence, including blood and pain. For it to be believable, anyone who didn't immediately accept the protagonist's warnings must remain entrenched in disbelief. As the werewolf devours his intestines, he insists that it's not real, that he can see the zipper in the fur, and refuses to use the silver dagger the hero gave him, because that's just 'playing into the myth.'