When in doubt, don't argue with anti-maskers. That's the recommendation from the CDC to retail and service employees. This week, the health agency issued new guidance to limit workplace violence that could be aimed at workers when enforcing their companies' Covid-19 safety procedures. The procedures that retail and service businesses have been advised to implement under CDC guidelines include enforcing mask wearing, social distancing and limiting the number of customers allowed in a business at one time. But the CDC warns that workers could be threatened or assaulted for employing these safety measures, describing violence ranging from yelling and swearing to slapping and choking the employees.