Diana Hernandez has one foot in the Ivy League, where she’s an assistant professor of sociomedical sciences at Columbia University’s Mailman School of Public Health, and another in the grittier streets of the South Bronx, the mostly working-class area where she lives. Walking down a Bronx boulevard the other day, she witnessed scenes much different from the TV news version of the coronavirus crisis, where suburbanites stuff payloads of squeezably soft toilet paper and price-gouged Purell in the back of luxury SUVs.Instead, Hernandez wrote that she witnessed Bronx shoppers at her local Dollar T...