ON FEBRUARY 28, 1974, Tony Shafrazi walked into the Museum of Modern Art in New York and spray-painted kill lies all in red across the achromatic surface of Picasso’s Guernica (1937), in protest of United States atrocities in Vietnam. The next day, his action appeared on the front page of the New York Times, as he had intended: Shafrazi had notified news agencies in advance. On October 14, 2022, nearly 50 years later, Phoebe Plummer and Anna Holland walked into the National Gallery in London, opened a can of tomato soup, and splattered it across glass protecting Van Gogh’s Sunflowers...