Guy Lodge Film Critic At the 1987 Conservative Party Conference in Britain, then Prime Minister Margaret Thatcher issued one of the most grimly memorable quotes of her career: “Children who need to be taught to respect traditional moral values are being taught that they have an inalienable right to be gay.” For many of us, it’s a line that now sounds so archaically out of step with contemporary life as to be comical — that “inalienable right” wording ironically appropriated by many a queer-rights cause — though you need only look at Florida’s recent Don’t Say Gay bill to know that Thatcher’s sentiments live among us still. A frank, piercing debut from British writer-director Georgia Oakley, “Blue Jean” is a Thatcher-era period piece that crisply evokes that climate of politically propagated homophobia without preserving it in amber: It effectively puts the past in tacit dialogue with the present.