I see what you mean and I understand how it's more serious than it sounds as first. However, a band shouldn't be able to lay claim to every version of demon hunter in media. Will they go after Wow for the class named such? How about the various animes with some variation in their title? Sure they can protect brand in a musical space, but that extends over to movies? When the movie title quietly literally describes exactly the protagonists?
You're right. They might be able to win this case, but shouldn't.