Time magazine is getting mercilessly mocked over an article about “the white supremacist origins of exercise” that claims that racism was the motivator for the fitness movement. The mag ran the eye-catching headline Wednesday based on a chat with history professor Natalia Mehlman Petrzela, whose lessons at New York’s The New School often focus on Black Lives Matter protests. In the interview, the self-styled “scholar, writer, teacher and activist” insisted that being fat used to be “desirable” — and the push to work out in the 20th Century was racism at work. The idea “that women should be lifting weights...