That the lynching party was relatively small and the witnesses in many cases were few does not eliminate the complicity of local officials and elites. Jail guards went off duty before the lynchers came, or did not put up a fight. State and local officials usually did not investigate the lynching and seldom prosecuted the lynchers.
There was an ideology that motivated the Southern (and other) lynchers: white supremacy combined with a redirection of Southern anger toward their failed secession attempt onto the African-Americans. The white supremacist beliefs derived from a form of Darwinism that applied the biologist's evolutionary principles to racial differences. This ideology, in a more virulent form, motivated the German Nazis. Until the 1920s, most Americans, even those who thought lynchings were horrible, believed that whites, especially Nordic whites, were the superior race.
Had Theodore Roosevelt or Calvin Coolidge sent Federal troops into the South to stop lynchings and protect black civil rights, they would have provoked a second civil war. In Coolidge's time, with the Ku Klux Klan having several million members in the Northeast, Midwest and West, as well as the South, the civil war would have had combat zones from Maine to California. Catholics, Jews, blacks, Indians, union members, and white liberals (both old style liberals like H.L. Mencken and Robert Taft and socialistic modern liberals) would have been arrayed against a probable majority of white Protestants. With tanks, machine guns, and warplanes, such a civil war would have made the 1861-65 troubles look like a barroom brawl.
The end of lynching and equal rights for African Americans had to await several decades as public opinion, even in the South, was swayed to oppose at least the crudest manifestations of white supremacy. After the 1920s, theories of the genetic superiority of Europeans were largely debunked by science. Southern politicians and businessmen recognized that the virulent racism of prior decades hurt the region's economy, keeping investment out. Losing millions of blacks to Northern cities diminished the South's labor pool and created a voting bloc in the Northern industrial states that pushed Northern politicians for Federal action against segregation. The horrors of Nazi Germany, the ultimate race based regime, disenchanted many from racist views. From the late 1920s through the 1950s, the number of lynchings declined dramatically. Those that occurred mostly took place in small towns, not in Dallas or Atlanta, and usually happened under cover of darkness.
By the 1950s, the South had changed sufficiently so that when Presidents Eisenhower, Kennedy, and Johnson sent Federal troops and lawmen into the region to end school desegregation and arrest white supremacists, there was no general uprising as there likely would have been at the height of the lynching era. Orval Faubus, Ross Barnett, and George Wallace blustered and proclaimed their support of segregation, but they did not order their respective states' National Guards to resist the Federal authorities. Neither did they call for armed uprisings in Little Rock or Birmingham. (There was one small insurgency at Oxford, Mississippi, where several thousand segregationists, led by retired Army General Edwin Walker, fought a force of Federal marshals attempting to desegregate Ole Miss. However, regular Army units soon routed the Rebel wannabes.)
Times changed, but it took over 30 years to do so.
I have used this discussion of American history to lead into consideration of the issues of a police-type response vs. a military response to the outrages at Fallujah, Iraq. This particular part of Iraq is a stronghold of anti-American sentiment. Do we really have the luxury of many years to win the hearts and minds of those Iraqis motivated by either Baathist or Muslim extremist ideology to abandon those beliefs? It appears that half-hearted measures, like sending Federal marshals into the South in 1924, would be futile. The only solution is a massive exercise in force to make the Iraqi elite and masses realize, as did the Germans post V-E Day, that resistance is signing one's death warrant.
In the immediate days after World War II, Nazi diehards, called werewolves, tried an underground resistance. The werewolves, when captured, were shot on the spot by Americans, Britons, and Russians alike. Resistance soon ended. Those Germans who were pro-Nazi, but not as fanatic as the werewolves, soon learned their lesson.
There is no substitute for victory.