Movie stars and the perils of the podium

THE DASHING 19TH CENTURY POET Percy Shelley once referred to artists such as himself as “the unacknowledged legislators of the world.” The notion that artists have a special platform—and a pressing duty—to shape public policy has never been far from creative minds, even as pop musicians elbowed poets aside as celebrities and movie stars superseded novelists. And perhaps that has never been truer than now, when a star from