No they're not saying desegregate prisons, they're saying that the assumptive requirement of prison desegregation points to how low the bar is for keeping prisoners safe.
Plenty of rape happens in male-only prisons and it doesn't even make the news. A significant portion of society believes that the threat of prison rape is an acceptable part of the punishment.
It would make more sense to segregate based on the nature of the crime, keep the sex offenders in specialised institutions away from less serious crimes