It would really be more of a humorous, random thing if the KKK adopted a highway. Can't you see yourself going down a road and you see "Adopt a Highway: Knights of the Ku Klux Klan Chapter in Burmingham"? I don't know about you but I'd laugh and probably crash into a tree from laughing too much instead of watching the road. It's not like they are going to be holding protest rallys outside of Rosa Parks High School or so. Which is a right given to them in the consitution. And a story nolt related to this thread.
Plus it wouldn't speak well of the KKK to leave another road unclean
As for the KKK themselves...well, they suck. Pure and simple.