Mark Zuckerberg has said Facebook allows its users to speak on equal footing with the elites of politics, culture and journalism, and that its standards apply to everyone. In private, the company has built a system that has exempted high-profile users from some or all of its rules. The program, known as “cross check” or “XCheck,” was intended as a quality-control measure for high-profile accounts. Today, it shields millions of VIPs from the company’s normal enforcement, the documents show. Many abuse the privilege, posting material including harassment and incitement to violence that would typically lead to sanctions. Facebook says criticism of the program is fair, that it was designed for a good purpose and that the company is working to fix it.