You had people in the North who didn't think slavery was a good idea. They wanted it to be abolished. Then you have the southerners who think that the states should be the one's who decide if they have slaves or not. In the 1800's, this was soon after the American Revolution, and they had just gotten out from under the hands of what they considered to be an unjust ruler. Now "rights" were the biggest talk.
This was a huge conflict for people in the north and the south. While black people weren't even necessarily welcomed in the north, the north still believed that they were humans, and that they should be treated as such.
After a lot of petitioning and arguing, you end up with the Mississippi Compromise. Although, this didn't really help, because soon we still had a civil war. Does this help at all?