Within hours of explosive sexual abuse allegations against labor leader César Chavez, officials at a California university took swift action and covered a statue of him. It is one of scores of monuments, city streets and schools nationwide that honor Chavez’s name and his labor movement legacy. Overnight, his name has become more of a stain. Some of the institutions and local governments started the process Thursday of erasing it. Officials in various cities are also moving to rename César Chavez Day, a federally proclaimed holiday on March 31, his birthday. The New York Times first reported Wednesday that it found credible evidence that Chavez sexually abused young girls.