"The enchanted Mjolnir was once a religious relic, and wielded by a staunch believer...."
Ummm, it certainly still would be a religious relic wielded by a staunch believer, as Thor is a god, who presumably believes in himself.
For that matter, Thor seems to know about vampires, but then says, "Though thou walk this night, never shalt thou see the light of dawn, unholy creatures!" They never would anyway, 'cause it would, y'know, destroy them.