The Counter Revolution of 1776 was a wild book. Early Amerikan settlers were absolutely terrified of slave revolts, to the point of daily cold sweats, but the only solution they found was to pass yet more draconian slave revolt laws. Chattel slavery seems to do something to the victim, like one is willing to risk death and torture in a slim hope of rebellion or revenge.
Lots (but not entirely all) of abolitionist sentiment was just a self-preserving fear of slave revolts that the slave states were dealing with on the regular.