In 1857, the solution du jour to the slavery problem in the territories was “popular sovereignty.” It wasn’t working very well, as the residents of Kansas could have told you. The Supreme Court decided to put an end to the issue by openly siding with the pro-slavery side regardless of public sentiment. As we know, that didn’t turn out too well.
Anti-abortion activists like to analogize abortion to slavery. For reasons I described years ago, that analogy really doesn’t work, but let’s go with it. Alito probably thinks Dobbs is the opposite of Dred Scott, because he has taken an issue that was mostly relegated to the courts and returned it to the political sphere: i.e., we’re back to “popular sovereignty.” In reality, however, Dobbs resembles Dred Scott in that the class of individuals in question was deprived of important pre-existing rights by an activist judiciary. Alito is more the new Taney than the anti-Taney.