Longshoreman Howard Keylor knew when to unload a ship and he knew when to refuse. A longshoreman for decades on San Francisco Bay, Keylor could unload the contents of a ship’s hold as fast as anyone on the waterfront. But he could also stand fast, lock arms, hold a megaphone and do nothing. That’s what he and his fellow longshoremen did for 11 days in 1984, when the South African cargo ship Nedlloyd Kemba came to the port of San Francisco, its hold full of fruit, wool and sugar.