Overpopulation panic is back. Concerns about a world too full of “filthy human children” motivated eco-terrorist James Lee when he held employees of the Discovery Channel hostage at gunpoint in September. But the deranged Lee is far from alone when it comes to worrying about overpopulation. The May-June cover of the progressive magazine Mother Jones asked, “Who’s to Blame for the Population Crisis?” British journalist Matthew Parris wrote an op-ed in September in the London Times asserting, “If you want to save the planet, stop breeding.” Parris further coyly suggested that we study “China’s example, for lessons good and bad.”...