I am no US history expert, but methinks that situation in the South looked a bit more complex. There was a brief period after the Civil War in which the poor whites and newly freed slaves were finding common political interests and a common ways to pursue those interests - to which the ruling classes responded by playing the "race card" in their all too common "divide and rule" strategy. Can anyone more familar with the US history correct that or supply more details (Michael Hoover?).
In more general terms, I 'd go as far as saying that there is no such thing as free willed racism, or bigotry in general. That is, people may hold prejudiced views of other social groups, but before those views solidify into racism, they must be constantly reinforced by formal and informal social institutions. Without such institutional support and reinforcement, the said views do not have a chance to develop into a coherent ideology and policy.
Since social instituions are usually controlled or at least heavily influenced by the ruling classes ("the class that has the means of material production at its disposal ... rules also as producers of ideas" -KM) - the responsibility for bigotry falls mainly on them. The pattern of elite sponsorship of mob violence in response to popular organizing is quite clear from the deep South, to Po valley, to California in 1930s, to Yugoslavia in 1990s.
Of course, after bigotry has been institutionalized, the ruling elite may look down with fake horror and say "Look how bigoted and irrational those common folks are! If it were not for our benevolent liberal rule, they would be at each other's throats."
Wojtek