Benjamin Braddock (Dustin Hoffman) is spinning among his parents’ friends in the living room of his commencement party, accepting hugs, congratulations and advice in the 1967 film The Graduate, when a party-goer grabs him by the arm and insists, “Plastics are the future.’’    “Plastics’’ became a popular one-liner of my youth, long after Rhett … Continue reading Valedictorians look backward, then turn attention to future