Why was the dred scott decision so controversial in the north?

Instead, in 1857, in the case of Dred Scott v. Sanford, the United States Supreme Court declared that all blacks — regardless of whether they were slaves or free men — were not and could never become citizens of the United States. The court also ruled that the 1820 Missouri Compromise was unconstitutional.Dec 13, 2010

Because the discoveries were some of the oldest human remains.