This is a deeply misleading explanation of American constitutional history.
The clause was demanded by Southern proponents of slavery as a way of enhancing their congressional representation. They wanted slaves to be counted as full persons but settled on three-fifths. People of African descent would have had no real rights either way. The inclusion of the clause greatly enhanced the South's political power and made it harder to abolish slavery. The clause was effectively eliminated after the Civil War by the Thirteenth Amendment.
"Some of the compromises we can look back and be proud of; some of those compromises we can't be very proud of. The three-fifths compromise, by which slaves were counted as three-fifths of a person, is not something any of us would applaud them for today," said University of Pennsylvania historian Richard Beeman in a 2011 interview.
Jackson, who was nominated over the weekend, has since taken a beating in the press for his many outside-the-mainstream positions and remarks. He also argued in 2011 that it was inappropriate for Obama to sit in a church where a pastor would bring up slavery.
"This is 2011. The issue of slavery was settled 146 years ago," Jackson said in the same statement. "For the President of the United States to sit in yet another church where the Pastor dredges up the past as if nothing has changed demonstrates either tremendously poor judgment or that Mr. Obama shares this sentiment. Either way, it is divisive and destructive, and the President should be above such associations."