“It is the very essence of art,' she [Hallie Flanagan:] told a group gathered in Washington . . ., 'that it exceed bounds, often including those of tradition, decorum, and that mysterious thing called taste. It is the essence of art that it shatter accepted patterns, advance into unknown territory, challenge the existing order. Art is highly explosive. To be worth its salt it must have in that salt a fair sprinkling of gunpowder.”