The pint-size soldiers of Gavin Hood's “Ender's Game,” the long-awaited adaptation of Orson Scott Card's YA sci-fi franchise starter, are dab hands at fighting off alien invaders, unreasonable authoritarianism and each other – though we have yet to see how well equipped they are to handle a real-world human rights boycott. In the last few months, the volume of the marketing for this would-be tentpole has been rivalled by the pop-cultural pushback against its creator: not Hood, of course, but co-producer Card, a sophisticated, audience-attuned storyteller who also happens to be a vocally homophobic loon. Would that Summit could write him out of the production and retitle it “Gavin Hood's Ender's Game” – or, indeed, “Lee Daniels' Ender's Game.” But them's the breaks.

 Why open on this purely circumstantial note? The situation is not of the film's making, after all – Hood's adaptation is even at pains to remove whatever evidence of the author's dubious personal beliefs had seeped onto the page. (Sure, it's just a coincidence that Card settled on the term “Buggers” for the alien race threatening to wipe out humanity.) Meanwhile, a boycott is the last thing “Ender's Game,” a carefully constructed, serious-minded commercial entertainment that treats its young audience with an unusual degree of intelligence, deserves.

At the same time, however, there's something inadvertently apt about a campaign this sincerely right-on against a film that could hardly be more righteous itself: “Ender's Game” isn't especially revolutionary in its one-against-the-system politics, but is distinguished – in the ranks of high-concept kid-lit adaptations, at any rate – by its sturdy, inquisitive moral compass.

Burdening children with the consequences of violence is increasingly commonplace in mainstream filmmaking these days – even the clean-scrubbed cherubs of “Harry Potter” were getting pretty tormented by the Deathly Hallows stages, while the extreme parable of “The Hunger Games” took its underage characters into a realm of post-”Lord of the Flies” bloodlust, albeit with PG-13 restrictions. “Ender's Game” sets kids on each other, too, but only as proxies in preparation for very adult warfare.

Interstellar battle looms between humanity and the tactfully renamed, insect-like extraterrestrial Formics – who have already struck once, with severe consequences. For whatever reason, the military is counting on only the planet's most precocious adolescents to defend our turf. The bulk of the film takes place at a kind of vacuum-sealed space-boot camp, where killing age is reached well before kissing age – Whitney Houston presumably had something else in mind when she implored us to teach the children well and let them lead the way.

Hood's brisk script – its pared-down backstory an unusual asset within the genre – leaves pleasingly open the question of why children are being made to fight these battles in the first place. Perhaps it's simply a natural evolution of present-day military practice: are these youngsters significantly less prepared for the worst than the teenagers sent to fight in the Middle East?

Perhaps the rationale of Harrison Ford's crusty commanding officer Graff is that young, malleable minds may be more receptive to the art of war – a receptive twist on the very claim conservative-minded scolds have been making since the advent of video nasties and the Nintendo generation. If so, Graff meets unassuming but stubborn resistance in the shape of Ender Wiggin (Asa Butterfield), the brightest and most strategically cunning of his recruits, and also – hardly coincidentally – the one least inclined to take his designated enemy at face value.

Guy Lodge is a South African-born critic and sometime screenwriter. In addition to his work at In Contention, he is a freelance contributor to Variety, Time Out, Empire and The Guardian. He lives well beyond his means in London.