One of the things Douglass resented about the U.S. in his day was that even most of the abolitionists in the Union states didn’t see blacks as equal to whites. These abolitionists wanted to end slavery, but they were perfectly content to treat freed and escaped slaves as second-class citizens in the Union.
Most Northerners wanted them expelled from the nation. Illinois passed a law forbidding blacks from settling in their states. I believe several other Northern states did so as well. Lincoln himself was an officer in an organization dedicated to getting blacks to leave the US.
At their core, today’s liberals have the same racial attitudes of the abolitionists that so disturbed Douglass.