Why Did Some Americans Want To End Slavery?

That was not and is not the way humans treat one another, it was a thing of control and trampling on the ego and self esteem of another race which is wrong no matter how you look at it and in time this nation will have to pay with life or limb, it was and is totally wrong, things that were done during that time will get you a jail sentence today.....Why would someone want to keep that way of life continuing? I would suppose more were against it than were for it, plus in this day in time I don't think blacks would lay down and roll over, most are saying I will be dead and in my grave before I will live as a slave, plus life as we know it nothing last forever....