This is not unlike the tribalism in Afghanistan. It is a true problem for the educated in Pakistan and the world at large.
Caste system, yes. Gang rape of innocent women, no.
Supposedly the police and lawyers are Muslim who are outraged and seeking prosecution, but whether these tribes practice Islam versus tribal justice and to what extent, is not clear to me. Islam enjoins compassion; indeed every Islamic epithet of Allah is "the Compassionate, the Merciful." One supposes if some hillbilly community of KKK members did some terrible deed that we must therefore condemn all of Christendom, too. The failure to adhere to religious morality in no way diminshes its excellence in preserving life and fostering happiness.