The name of the art exhibit, “Sensation,” sponsored by the Brooklyn Museum of Art in the fall of 1999 was apt—it did cause a sensation, not just in New York, but across the entire country. The exhibit contained several pieces of controversial art, the most well known of which was Chris Orfili’s “Holy Virgin Mary,” a portrait of a black Virgin Mary decorated with elephant dung and pornographic photos. Rudolph Giuliani, the mayor of New York, was so disgusted by the “sick stuff” in the exhibit that he refused to pay the city’s $500,000 monthly subsidy to the museum unless it cancelled the exhibit.

Giuliani contends that artists are free to create offensive work such as “Holy Virgin Mary,” “but to have the government subsidize something...