Who among us hasn't stumbled headfirst into a violent coup attempt involving millions of dollars of black market weaponry? That's the argument Robert Granieri, multimillionaire cofounder of trading firm Jane Street, is invoking after being caught funneling hoards of cash to an opposition party in South Sudan. The funding allegedly included millions of dollars in backing to purchase rifles, Stinger missiles, bulletproof vests, and grenades meant to topple South Sudan?s...