MUMBAI — In most cities of South Asia, hidden beneath the grime and neglect of extreme poverty, there exists a little Somalia waiting to burst out and infect the body politic. This netherworld, patrolled and nourished by criminals who operate a vast black-market economy, has bred, in Mumbai, a community that has utter contempt for the state, because it knows that its survival depends on corrupting the police. Like underground magma, that underworld has now burst into the streets of Mumbai.