Touchy feely drama seven generations afterward do not speak to the laws and precedents of the early to mid 19th century. I would rather not defend the Dred Scott decision but it certainly was correct under the laws as they stood at the time. Hence the need for the 13th, 14th and 15th amendments to the constitution, to provide the legal foundation for the new order.
The Scott decision was wrong even at the time, as it claimed blacks had never been and never could be citizens of the United States.
In fact, blacks had at various times been full citizens of various states, including at the time when the Constitution was implemented and at the time of the Scott decision.
Thus the decision was based on factual errors. There was also nothing in the Constitution at the time giving the Court, or Congress for that matter, the right to decide who was and was not a citizen of the United States, with exception of immigration laws. That power, with regard to persons born in the US, had previously been left to the States, with a citizen of a State automatically considered a citizen of the United States.
Taney arrogated to the Court not only the right to decide who was a citizen as of 1857, but who could EVER be a citizen. This rather breathtaking assumption of power to the federal government is amazing in those who theoretically supported states’ rights.
It is interesting that all the southern demands leading up to the war required expansion of federal power: federal protection for those taking slaves into the territories, federal enforcement in the states of the fugitive slave laws, federal determination of who was or was not a citizen of the United States.
Most legal critics, as opposed to social critics, of Scott v Sanford point to Taney's decision to go well beyond what was needed. He could simply have asked his brethren to declare that as a slave Scott had no standing to come before the Court. Or he could have turned to the prior decision in 1850 that such cases of itinerant slaves would be decided by the courts of the state of origin. In this case Missouri. But Taney was searching for a final act that would end the legislative standoff over slavery and, in his view, allow the government to get on with other business.
While an act of judicial activism Taney's decision was an upholder of states' rights. Only Congress could deny a slaveowner of his property and only on tterritory governed by Congress. Massachussetts was as free to declare slavery anathema on its soil as Alabama was to embrace it.