Kafi Dixon is one of the producers of "A Reckoning in Boston" and a subject of the film. (Courtesy) Late one night in an adult education classroom in Dorchester, Kafi Dixon compares the toll of living in an environment that upholds white supremacy to a “slow drip, drip, on a hard stone.” Her comment prompts a burst of discussion. One student ups the comparison to a trickle and the group shares a laugh when another adds, “Turn that faucet off!” Drawn to the intimacy and transformative potential of the Clemente Course in the Humanities -- designed to give adults with limited financial resources a chance to rigorously study literature, history, and philosophy — Newton filmmaker James Rutenbeck thought he’d make a documentary full of scenes just like the one described, inspired by students like Dixon. And in fact, he tried.