Three bad ideas are fueling the backlash against J.K. Rowling. The first, that a human’s biological sex can be changed. The second, that believing otherwise tarnishes one’s character. The third, that artists must conform entirely to leftist standards lest their work be deemed unworthy of consumption. Each of these bad ideas is rooted in notions both ascendant and troubling.Rowling, an outspoken leftist, made headlines just about everywhere on Thursday for tweeting in support of Maya Forstater, an academic who lost her job at a think tank over tweets affirming the reality of biological sex, including, “men cannot change into...