The U.S. Supreme Court let stand on January 10, 2005 a ruling that the Ku Klux Klan can take part in Missouri's 'Adopt-A-Highway' program in which volunteers pick up trash along the road and the state puts up a sign thanking the group.
This sign from Interstate 55 is from December 1999 believe it or not, which makes all those Jesus is Coming Soon signs seem tame by comparison.
I don't know about you, but if I saw a group of hooded Klansmen picking up litter on the side of the highway, I'd say that's a good cause for pollution and/or a good old fashioned hit-and-run.