Requires cultural change:
While rules and penalties can and do deter wrongdoing, broader social changes do a lot more. In the 1960s, drunk driving and littering were winked at even amongst the "respectable" classes: public education campaigns, new laws, and cultural shifts that resulted made both of them socially unacceptable and, as a result, the roads are safer and public places cleaner than they were. The same thing needs to happen with prison rape. Until it does, however, the extraordinary prevalence of sexual abuse in prison will remain a great moral failing of modern America.