Kate Beaton is the queen of funny historical comic strips. This one (click here for a fuller view) is on the making of medieval films.
On the subject of historical inaccuracy in film, she has an interesting comment along the bottom:
“It's silly to think that movies aren't ‘important’ because they're entertainment, movies are the way most people come across with representations of histories they don't know much about! So I can't blame anyone for caring that they get the details right.”
It reminded me of a friend who said to me, not long ago, that he hates whenever people dismiss a movie as being “just a movie”. The reason is because, whether we like it or not, film shapes the way we perceive our world, up to and including periods of history. For an archaic but fascinating perspective, read this article entitled "The Cinematograph and the Imagination". I found it in an old Jesuit periodical dated to 1915. Even with those old, jerky, soundless films the essayist must have referred to in his "experience" on the Titanic, I think he may have a point or two.
I’d conclude this thought by saying that whether or not Vikings actually wore horned helmets is not that big a deal, but a movie that attempts to treat the medieval period seriously, while totally disregarding the customs and mores of that era (for example, Kingdom of Heaven’s openly agnostic hero preaching about religious liberty to a crowd of 12th century peasants), is a damnable piece of trash.