That claim is true, FWIW, Democrats did own slaves from 1828-1865. The phrasing doesn't deny that non-Democrats owned slaves prior to the existence of the Democratic Party, or for that matter that some Whigs owned slaves at the same time Democrats owned them. The other claim is the dubious one - it's not clear what would constitute libertarianism in the context of antebellum America.
The main problem, though, is that it's irrelevant to anything involving 21st century politics, because the parties and relevant issues have changed so as to be entirely different from anything they were in the 19th century. Why bother stating it?
The main problem, though, is that it's irrelevant to anything involving 21st century politics, because the parties and relevant issues have changed so as to be entirely different from anything they were in the 19th century. Why bother stating it?