The Dartmouth Civil Liberties Union tonight will show “Unconstitutional,” a film produced by liberal activist Robert Greenwald about (what else?) the PATRIOT Act. Greenwald has produced a series of partisan niche “films” in the past several years: “Uncovered,” a liberal flick decrying the Iraq war; “Outfoxed,” a rather predictable production about how Fox News is taking America back into the stone age; and “Unprecedented,” about how Republicans are undermining democracy.