“From the vantage point of the newsroom, the first story is almost never the full story,” writes Jelani Cobb. “You hear stray wisps of information, almost always the most inflammatory strands of a much bigger, more complicated set of circumstances.” The dean of Columbia University’s Graduate School of Journalism in New York could be reflecting on the recent killing of the racist provocateur Charlie Kirk. In fact, he is thinking back to Trayvon Martin, a 17-year-old African American student from Florida who was shot dead by a white Latino neighbourhood watch volunteer in 2012. “The Martin case – the nightmare...