Zinn brings up some pretty strong evidence of near constant attempts at violent insurrection among slaves as well as organized, brutal repression and reprisal of any spark that might catch

Gerald Horne covers this in depth in The Counter-Revolution of 1776. Can't remember if it's that from that book or another, but there were also abolitionists at the time of the American Revolution, as well as freed black people who could (and did) tell the white aristocracy exactly what slavery was.