If they meant that they would have written it that way.
They did. Today some folks are trying to interpret the language differently than originally intended.
But that doesn't matter because the admin is doing it in bad faith.
What bad faith? That interpreting "subject to the jurisdiction of the US" (or whatever the actual language is, didn't look it up) is not referring to those in the US legally? That's not bad faith, that's an honest interpretation to be decided by the Supreme Court. It is arguably what the original authors meant, and how it was read in those days.
But basically your "Democrats racist because 1860s" is just deeply deeply unserious and should be ignored.
Wrong. 1860s. 1880s. 1900s. 1920s. 1940s. 1960s. And starting in the 1920s it the was the democrats nationally, not just in the south. The klan was national by that point, and its strong influence within the Democratic Party also national. The republican courting of southern democrats in the 1960s and 70s was law and order based, not klan belief system based. It was an era of violent protest, where marxist/maoist inspired radicals (its what they self identified as) fomented violence.