One of the sleaziest documentaries to arrive in a very long time, “Expelled: No Intelligence Allowed” is a conspiracy-theory rant masquerading as investigative inquiry.

Positing the theory of intelligent design as a valid scientific hypothesis, the film frames the refusal of “big science” to agree as nothing less than an assault on free speech. Interviewees, including the scientist Richard Sternberg, claim that questioning Darwinism led to their expulsion from the scientific fold (the film relies extensively on the post hoc, ergo propter hoc fallacy  after this, therefore because of this), while our genial audience surrogate, the actor and multihyphenate Ben Stein, nods sympathetically. (Mr. Stein is also a freelance columnist who writes Everybody’s Business for The New York Times.)

Prominent evolutionary biologists, like the author and Oxford professor Richard Dawkins  accurately identified on screen as an “atheist”  are provided solely to construct, in cleverly edited slices, an inevitable connection between Darwinism and godlessness. Blithely ignoring the vital distinction between social and scientific Darwinism, the film links evolution theory to fascism (as well as abortion, euthanasia and eugenics), shamelessly invoking the Holocaust with black-and-white film of Nazi gas chambers and mass graves.

Every few minutes familiar  and ideologically unrelated  images interrupt the talking heads: a fist-shaking Nikita S. Khrushchev; Charlton Heston being subdued by a water hose in “Planet of the Apes.” This is not argument, it’s circus, a distraction from the film’s contempt for precision and intellectual rigor. This goes further than a willful misunderstanding of the scientific method. The film suggests, for example, that Dr. Sternberg lost his job at the Smithsonian’s National Museum of Natural History because of intellectual discrimination but neglects to inform us that he was actually not an employee but rather an unpaid research associate who had completed his three-year term.