You should probably distinguish between antislavery and abolition; the abolitionist movement was never a popular movement and many norther blacks had nothing to so with it and focused their politics on self improvement or bigotry in northern society. In the south, abolitionismt literature and organizing was rare and often veiled in deep secrecy. Combine that with the limited political freedom of enslaved people and you had few black southerners who could directly join the abolitionist movement. Opposition, however is rare , and mostly it was the few and rare black slaveholders who would have been opposed to abolitionism.