[Sherman Logan]

Anti-slavery abolitionists were outraged that a slave on free territory could now be forcibly removed by the law of the land, back to his or her owner in a slave state.

The DS decision didn't initiate this. In fact, return of slaves to their masters was part of the Constitution.

The DS decision upset people in the North because it made it impossible to prevent the spread of slavery. And because many believed that it would be used as a precedent to make it impossible for free states to prevent slavery in their own bounds.

[Desron13]

Anyone that thinks that they can own another human being is a complete idiot. The very fact of being human makes slavery impossible. Those that attempt it are by definition subhuman animals.