The Ku Klux Klan was founded in 1865 by racist whites seeking to fight against radical Republican efforts to reconstruct the South. The KKK targeted both blacks and white Republicans; they even targeted some Southern white Democrats who weren't sufficiently anti-black. The KKK's argument: Blacks, by their mere presence and attempts to participate in the political process, were destroying the dignity of the white South.
The radical Republicans in Congress fought the KKK tooth and nail; in the early 1870s, they passed the Force Acts, designed to destroy the KKK once and for all. Those acts allowed the president to use the federal military to enforce the 15th Amendment. It nearly did the trick. Within a few years, the KKK had been virtually wiped out.
Then came the election of 1876. Not only did Southern Democrats -- often closely allied with the KKK -- win back South Carolina, Florida and Louisiana, they also helped broker an election deal with Republican Rutherford B. Hayes. Samuel Tilden won the popular vote, but Hayes won a majority of one vote in the Electoral College through a series of complex machinations. A constitutional crisis ensued. It was solved when Hayes essentially promised to end reconstruction efforts and withdraw federal troops from the South in return for Democratic support for his presidency. Offshoots of the KKK quickly returned, restoring the South to a state of horrific oppression and segregation; it uprooted the progress made since the end of the Civil War. Southern Democrats instituted Jim Crow and revivified both violence and racism on a massive scale.
The moral of this story is simple: Racial violence can only flourish with the approval or apathy of federal, state and local government.
Fast forward 132 years. Racial violence is becoming a norm around the nation. The city of Oakland, for reasons both racial and economic, has announced that it will stop using police to investigate grand theft, burglary, car wrecks, identity theft and vandalism. The Justice Department is suing the state of Arizona for cracking down on illegal immigration -- a blatant attempt by the Obama administration to woo Hispanic voters by making it more difficult for Arizona law enforcement to crack down on Hispanic illegal offenders. The Obama Justice Department has also dropped an investigation into the New Black Panther Party for voter intimidation, despite the fact that videotape shows members of the New Black Panther Party wielding clubs outside a voting place.