Why did Stephan Douglas support the Kensas-Nebraska Act and why was that a problem for those who did not like slavery?

Douglas thought that the people of each new state should be allowed to vote on whether it should be slave or free. This looked like a reasonable common-sense alternative to the various Compromises that had all broken down.

The Abolitionists did not like the idea, because it could have allowed the creation of new slave-states.