There is an angel at the Bethesda Fountain in Central Park, complete with pigeons perched along both wings; a figure that cries out as a metaphor for the life and times and ineradicable idealism of Tony Kushner, the playwright whose “Angels in America”—loved by many, overrated to some—gained him the Pulitzer Prize in Drama in 1993, when he was a still boyish 37 years old.