LOL - I got that info from an African-American History webpage. Northern racism is a well documented fact of history. Except by hatemongering revisionist liars like that idiot Jaffa, of course.
Northern racism is undisputed. But it was not the source of, or the inspirtation for, the southern Black Codes and Jim Crow laws. The south had been enacting such laws for generations. You didn't need the North for that.