We use the term when another cultural group is not willing to talk freely to an anthropologist

The term you might be searching could be 'Ethnocentrism', given when a member of a cultural group believes to own their culture, to have superiority over the rest of cultures. Furthermore, they presuppose to have the exclusive right to judge the norms, traditions and behavior of the other groups. As an anthropologist studies these features of the human race, they are not willing to talk them.