How did the development of a violent mini civil war in the territory of kansas demonstrate a fatal flaw in stephen douglas's popular sovereignty doctrine that the people of each territory should settle the slavery question for themselves?

Stephen Douglas hoped when pushing the Kansas-Nebraska act that the everything would be settled democratically, without violence by the settler that would be impartial but unfortunately this was at the same time the fatal flaw of the act. People misunderstood the act which led to anger by the southerners and the subsequent retaliation by the northerners as well as the creation of two governments in Kansas one that was elected on fraud and other that was not legal.  

to act quickly in times of danger to the united states

because you have to act quickly if you want to live/survive.