No - this is not a democracy - it's a constitutional republic. If disputed, the Supreme Court can decide the issue, but otherwise, why have a requirement against prejudice?
If he wished to move to a territory that prevented slavery then he was free to do so but without his chattle. He could leave them behind in Alabama, sell them, give them away, whatever. The government was not taking them away from him, it was not denying him of his life or liberty or his ownership in slaves. But Congress was within its power to tell him that he could not take them into a territory.
I disagree. Remember the 7-2 Dred Scott decision?
I do, and I believe that had the matter been left to be peacefully settled then future cases would have clarified the court's decision. Many people believed that the court overstepped the bounds of the issue before the court. The southern side must have suspected that the decision wouldn't stand since they chose the path of rebellion.