Never lose your cool. That seems to be the mantra under which directors Reed Cowan and Steven Greenstreet operated in the making of this documentary. The film contains enough inflammatory information — about the efforts of the Mormon Church to ban gay marriage in California — to send any supporter of marriage equality into a rage. To their credit, the filmmakers present their story in a calm, even manner, wisely allowing the passions of their subjects to carry the emotional weight of the film.

They open with a bit of grainy video displaying a one-shot of an unrecognizable man, as a voice — presumably his — tells his congregation that they are “a mighty army.” From this ominous opening, the scene shifts to June 2008, on the first day that same-sex couples were allowed to marry in California. Unfortunately, in life, as in art, the exhortation of that “mighty army” came before those marriages: The seeds of Proposition 8, the ballot initiative that in November of that same year amended the California State Constitution to define marriage as being between a man and a woman, were long since planted before that happy day in June.

In 8: The Mormon Proposition, Reed and Greenstreet set out to show just how instrumental the Mormon Church was in the creation, promotion, and eventual passage of that initiative, a fact the Church went to great lengths to downplay or even hide. Dustin Lance Black, Oscar winning screenwriter of Milk and Emmy winner for his writing on Big Love, narrates the film, and though he himself grew up gay in a Mormon household, his inflections never carry a subtext of commentary. He’s here to read Cowan’s words, and, just like the filmmakers, he knows not to upstage the obvious onscreen emotion, which cover a wide range of highs and lows.