Ing says "Some of these early immigrant workers were blackbirded victims of human trafficking, identified not by name but by bango (slave tag) numbers."

Wow.  Bigtime demagoguery, as suitable for a politician who thrives on it.  Chinese, Japanese, Filipinos and others came all the way to Hawaii to find what they regarded as a good job at good wages -- they were fleeing hopeless poverty and unemployment in the places they came from.  Some liked plantation life so well that they brought picture brides to join them here rather than returning home.  Life here was hard; life back home was far worse.  The bango tags were not slave tags -- they were the easiest way for an illiterate worker to make sure he got paid for the correct amount of produce he harvested even though he could not write his name.  If you think plantation workers were oppressed and exploited, blame King Kalakaua for licensing the plantations and approving the labor contracts.  Kalakaua profited greatly from Asian labor.