Our so-called conservatives, who have cut all ties to their own intellectual moorings, now espouse policies and personalities that would get them laughed out of Periclean Athens. The few conservatives still able to hold up one end of a Socratic dialogue are those in the ostracized libertarian wing — interestingly enough, a group with a disproportionately high representation among fans of speculative fiction.

The less politicized majority, who perhaps would like to draw inspiration from this story without glossing over the crazy and defective aspects of Spartan society, have turned, in droves, to a film from the alternative cultural universe of fantasy and science fiction. Styled and informed by pulp novels, comic books, video games and Asian martial arts flicks, science fiction eats this kind of material up, and expresses it in ways that look impossibly weird to people who aren’t used to it.

Lack of critical respect means nothing to sci-fi’s creators and fans. They made peace with their own dorkiness long ago. Oh, there was momentary discomfort around the time of William Shatner’s 1987 “Saturday Night Live” sketch, in which he exhorted Trekkies to “get a life.” But this had been fully resolved by 2000, when sci-fi fans voted to give the Hugo Award for best movie to “Galaxy Quest,” a film that revolves around making fun of sci-fi fans.

The growing popularity of science fiction, the rise of graphic novels, anime and video games, and the fact that geeks can make lots of money now, have given creators and fans of this kind of art a confidence, even a swagger, that — hard as it is for some of us to believe — is kind of cool now.

Video games have turned everyone under the age of 20 into experts on military history and tactics; 12-year-olds on school buses argue about the right way to deploy onagers and cataphracts while outflanking a Roman triplex acies formation. The near exhaustion of Asian martial arts themes has led a small but growing number to begin reconstructing, or imagining, the forgotten martial arts of the West. And science fiction, by its nature, has had to equip itself with a full toolkit for dealing with alien cultures, mindsets and landscapes.

Which is exactly how the creators of “300” approach the Spartans and the Persians. The only people in the film who don’t seem as if they came from another planet are the Arcadians (non-Spartan Greeks), who turn tail once the battle becomes hopeless.

Classics-based sci-fi is nothing new. To name the most recent of many examples, the novelist Dan Simmons published “Ilium” and “Olympos,” science-fictional takes on Homer. When science fiction tackles classical themes, the results may look a bit odd to some, but the audience — which is increasingly the mainstream audience — is sufficiently hungry for this kind of material (and, perhaps, suspicious of anything that’s overly polished) that it is willing to overlook the occasional mistake, or make up for it by shouting hilarious things from the balcony. These people don’t need irony or campiness self-consciously pointed out to them, any more than they need a laugh track to enjoy “The Simpsons.”