LOS ANGELES — Blasting billionaires as “oligarchs” whose “greed and arrogance and moral turpitude” threatens American society, Bernie Sanders rallied support here Wednesday night for a proposed wealth tax roiling politics in California. “Do you know what the most significant addiction crisis in America is today? It is the greed of the billionaire class,” the Vermont senator and progressive champion told a boisterous crowd in a blistering speech at the Wiltern Theatre in the city’s Koreatown section.