This is not true, or is only partly true depending on which KKK you are talking about. The original group formed in the 1960s as an anti-reconstruction organization and used terror tactics to chase politicians and businessmen they didn't like out of certain communities in the South. It didn't last long though and was disbanded in the early 1870's.

The 'second' Klan was originally a merchandizing effort surrounding the movie "Birth of a Nation." It quickly turned into an actual political organization which adopted the white nativist views which were in vogue at the time. It was largely anti-immigrant focusing on Catholics, but also targeting Jews and Eastern Europeans.

It's worth noting that in all of it's incarnations, the Klan was racist and anti-black. It wasn't until the 1960s that this became the center-point of their politics, but it was always there.