With metronomic regularity, some well-motivated billionaire announces that he wishes the government would increase his taxes. The latest entrant is Eli Broad. Writing in The New York Times, Broad praises private philanthropy and the capitalist system "that's yielded some of the greatest gains in prosperity and innovation in human history." Still, he concludes, "I simply believe it's time for those of us with great wealth to commit to reducing income inequality, starting with the demand to be taxed at a higher rate than everyone else."Some pundits might mock Broad, pointing out that nothing is preventing him from sending bigger checks...