He is different from the antebellum South because he believes in the protection of invidual rights, equal protection of laws and due process, under the 14th Amendment.
The principle of Federalism is for a “libertarian” federal government. With the States operating as laboratories (as described by Brandeis) and competitors, and people choosing where to live with their feet. As a check on States abusing their power over individuals, the federal government will protect individual rights, unequal treatment, and violation of due process. But so long as States avoid those issues (and a few others outlined in the Constitution) they should be allowed free reign (see the 10th Amendment).