Ezra has a good post on labor's historical difficulty in the South. I would also add that the central cultural conflict in the Reconstruction South between former Confederate planters and Northern capitalist carpetbaggers was not one divided on the issue of organized labor.
The carpetbaggers were laissez-faire economic liberals who expected the invisible hand of the market to lift the freedmen out of poverty. When this turned out not to be the case, the disillusioned capitalists mostly gave up rather than rethinking their ideas, and the only potentially labor-sympathetic allies of abolition, white yeomen farmers, saw their wages plummet as they were stranded in competition with sharecroppers.
And thus did folks like Andrew Johnson, who started out squarely opposed to the Confederacy and the evils of slavery, likewise become enemies of Reconstruction. And any nascent support for labor was swallowed up in the conflict over race.