While the rules of teenage dating and the exigencies of the marriage market are compelling explanations in themselves, other powerful forces play their part in making girls and women into the enforcers of female virtue. Among them, none is more significant than the phenomenon among individuals in any powerless group. It's this that helps to explain the behaviour of the black police in South Africa, of the colonial Indians who adopted English manners and mores, of the Jewish police in the nazi death camps, and the girls and women of whom I have been speaking. By identifying with the powerful, the disempowered achieve a measure of safety, at least for a moment. By doing the bidding of those in power, they become a necessary part of the system, useful so long they serve to contain the stirring and strivings of the oppressed. By making the rules and values of their oppressor their own, they separate themselves from the rest of the group and, temporarily at least, assuage the pain of their stigmatized status.
Lillian B. Rubin Erotic wars