Yes, actually this is legal. An employer can set the terms and conditons of the workplace much as it sees fit; this includes requiring an employee to purchase a company product. This is known as "at will" employment. For their part, an employee can comply with their employer's request, complain and risk termination, or quit. The foregoing holds true unless such an action violates an employment contract or union agreement. Also, the employee's treatment must not constitute some form of legally actionable discrimination (which it does not appear to).