Aren't you going to cite that dead professor who told you that way back when? Please explain 250,000 members of the American Anti-Slavery Society by 1838. Did none of them actually care about the plight of slaves. And if that was the case, why was the south so afraid of them?
In four words, "Nat Turner John Brown".
About 180,000 people died in the Haitian slave revolt.
In 1838 there were probably about 6,000,000 people in the South, half of them slaves.