There’s a double-edged character to “Constantine’s Sword,” a documentary essay in which James Carroll, the former activist Catholic priest turned author-provocateur, not only traces the history of anti-Semitism within the Christian tradition (especially the Roman church) but also ties it to the broader issue of the unholy alliance between church and state. And Carroll also gives his argument a more personal touch by connecting it to his own family history via his relationship with his father, an erstwhile FBI agent who entered the military and eventually became commandant of the Air Force Academy in Colorado Springs.

It’s there that Carroll begins his essay, based on his book of the same title. He returns to the school both to recall his adolescent dream to become a cadet—trumped by his decision, impelled by the religious intensity of his family (especially of his mother, a devotee of St. Helena, who supposedly found the so-called true cross), to enter the priesthood—and to investigate reports that the academy has become a hotbed of anti-Semitism. He finds that both students and faculty have fallen under the influence of Ted Haggard, the charismatic pastor of a nearby evangelical megachurch, whose proselytizing has become a powerful force in the academy and led to an outbreak of anti-Semitic incidents. (Haggard, who has since fallen from grace as a result of his dalliance with a male escort, is here interviewed in his pre-scandal days, when he’s tough-talking and sassy; and Jewish cadets discuss the treatment they suffered at the hands of those whom his message affected.)

To find the roots of this contemporary circumstance Carroll travels to Europe and the distant past, identifying the conversion of the Emperor Constantine—the son of the very Helena whom his mother revered—as the salient event in the transformation of Christianity from a persecuted sect to an official creed that could use the power of the state both to expand as an institution and to repress those of different beliefs. It’s from this that Carroll takes the title of the film, describing Constantine’s order to his soldiers to use their swords to form the sign of the cross in the deciding battle at the Milvian Bridge as a metaphor for how Christianity became a force of persecution itself. From this point he traverses various locales and uses interviews, texts (some recited by such actors as Eli Wallach, Liev Schreiber, Natasha Richardson and Phillip Bosco) and artwork to describe episodes—including, of course, the Spanish Inquisition and the Nazi era—in which Christian anti-Semitism in particular was expressed, concentrating on the Catholic Church (and the papacy) but, as the Colorado incident shows, spreading a wider net as well.

“Constantine’s Sword” is in essence a polemic, told from the perspective of a man whose disillusionment with the positions of his church (made evident especially during the years of the Vietnam War, against which he was a passionate advocate—much to the distress of his father) led him to leave the clergy. But it’s a polemic delivered with an attitude more of sadness than anger. And by presenting the narrative as a personal journey of discovery, Carroll and writer-director Oren Jacoby give it a human dimension—in much the same fashion as Michael Moore’s cinematic essays, though with a far milder, less jocular tone.

Technically proficient and crisply edited by Kate Hirson, “Constantine’s Sword” will doubtlessly distress some ultra-conservative Catholics with its emphasis on the long-overdue revision of Catholic doctrine regarding Judaism in the decrees of the Second Vatican Council, its recognition of the efforts of John Paul II to alter Catholic attitudes, and its suggestion that Pope Benedict XVI has not so subtly reversed Vatican policy on these matters. But though Carroll’s presentation is unquestionably oversimplified (as could hardly not be the case in a film that covers so massive a topic in little more than ninety minutes), his points are well taken and worthy of serious regard, and his picture is useful as a means of potentially bringing them to wider attention than they’ve previously received.

And though as long ago as the sixteenth century Menno Simons showed the problems an alliance between church and state poses, the situation in Colorado Springs proves that the pernicious use of government power to further religious aims continues to be a danger—in the United States and throughout the world.