Greg, of course there were those who were against slavery in both the north and south. My maternal great-grandfather,a Presbyterian minister , was among their number.
And of course there was racism. You cannot keep people enslaved if you don't feel inately superior to them and that was a prevalent attitude on both sides of the M/D line.
Abolitionists were looked down upon in the North. They called them Copperheads. I'm not sure of the origins of the word.
They had little sympathy or political power but were quite vocal or as vocal as the communications systems of the time would allow. But please don't think that the Abolitionists felt that the freed slave would be their equal. Some sort of back-to-Africa scheme was favored by some, while others were simply against slavery on principle with no egalatarian motives.

troll