Pablo Eisenberg writes that museums ought to stop whining about losing one of their tax breaks. “Most other charitable gifts don’t come with the flexibility and big write-offs available for artworks. What’s more, the museum directors dismiss the fact that only about 10 percent of all donations of art are accomplished through fractional giving. And it paints the restrictions on fractional giving as earth-shattering, as though the end of the museum world is about to unfold. What palpable nonsense.”