ASSAULT MADE TO A CASHIER BY A CUSTOMER

While shopping with my sister a customer attacked the cashier. 1. Telling her she's here to work 2. As the cashier was handing the customer her change along with her slip the. Customer slapped her. Attacking the poor cashier I feel the customer had no right to attack the cashier and for the mere fact that the cashier kept quiet the customer took advantage. The customer was pulled to the side, where the manager Clementine promised the cashier a warning and a threat that she will loose her job, such job ethics?? Really?? Has the world reallly come to a point where someone can be attacked by the customer and the manager can threaten the staff member instead of resolving the matter. I'm honestly begining to question the management skill that was offered to this manager.This rule of the "customer is always right" is nonsens, those cashiers are also human not slaves they are only human when working on the till and bringing in money to the company's. Can i please have a detailed description of the companies objectives emailed to my email adress and how the staff members should be treated. Within 24 hours.