Following in the footsteps of Al Gore, who was instrumental in spotlighting climate change as an imminent threat in “An Inconvenient Truth,” economist Robert Reich—who served as Secretary of Labor in the first Clinton term—addresses the issue of growing disparity in income between the wealthiest Americans and the struggling middle class in a similarly didactic, monitory documentary. But “Inequality for All” isn’t just a moralistic tract that treats the matter as one of simple ideological principle; it presents the subject in terms of economic theory, arguing that the economic wellbeing of the middle class is essential to the wellbeing of the entire economy and to the workings of the democratic political system, meaning that the stagnation, even deterioration, in the condition of the country’s working families is a betrayal of the American dream and an existential threat to the nation as a whole.

In truth there isn’t much that’s new in Reich’s presentation, which delivers the same message he’s been preaching for years. In fact, a goodly portion of the film simply records portions of a class on “Wealth and Poverty” he teaches at the University of California at Berkeley. (It’s obviously a popular course, filling a large lecture hall with enthusiastic students.) But Reich is an engaging instructor who avoids jargon and, using graphs that set off the historical data in illustrative form, makes what might have been arcane quite accessible. He’s especially successful in using references to his diminutive size to disarm potential hostility in his listeners, and avoids treating the people he talks with condescendingly, as so many academics do. That, along with the biographical material the film provides periodically as background, makes him very hard to dislike. So too does the fact that he’s critical of himself and many of his liberal colleagues (including presidents) for their failure to address the problems he diagnoses seriously enough, while bemoaning the polarization of political discourse that had made confronting such fundamental issues nearly impossible.

Reich also personalizes the issues he raises—which proceed from his basic economic message to the corrupting influence of big money in politics, a problem he identifies with the explosion of lobbying and portrays as being astronomically worsened by the Supreme Court’s decision in Citizens United—by going beyond abstract argument to give real people the opportunity to tell their own stories. Two middle-class families are introduced as examples of how that segment of society has suffered over the past three decades. In one case, the husband lost his job when his employer Circuit City went under and the bank foreclosed on the family’s condo, forcing them to move in with friends and live hand-to-mouth. In the other both partners have jobs, but they still have trouble paying the bills, let alone saving anything. As a contrast Reich includes observations by Nick Hanauer, a multi-millionaire who agrees with the film’s populist argument, deriding those who call people like him “job creators” as a smokescreen to hide the reality that their driving goal is pursuit of their own ideological agendas (and tax policies). The “Occupy Wall Street” movement is also introduced as a symptom of the anger felt by many about how the system seems rigged against their interests.

“Inequality for All” basically constitutes a liberal jeremiad, but it’s one presented with civility, good humor and a human face as well as impassioned conviction. In that it’s an accurate reflection of Reich’s personality, and it leaves one wishing more of us had character traits similar to his.