How did the ruling in Dred Scott V Stanford increase sectional division?

In 1857, a slave who had sued his owner for freedom, based on being held a slave in a free state, was soundly defeated based on a Supreme Court ruling, because according to Justice Roger Taney, no black whether they were free or a slave was a citizen of the United States, and therefore, couldn't sue. Abolitionists were incensed by the ruling. The decision increased sectionalism and led to the Civil War.