I think it's safe to say they openly and bitterly resented it. To them, Reconstruction meant being readmitted to a Union they had fought so hard to leave. It meant being humiliated through occupation by, to them, a foreign army. It meant slavery was gone for good, even if they creatively found ways to reinstate it in everything but name. It meant watching African-Americans get elected to Congress from some of the most pro-slavery states in the South.
Because of this, they resisted in whatever ways they could. The Klan was formed in 1865, first as a veterans organization, then as a terrorist group aimed at suppressing black freedoms and intimidating teachers in new black schools. They acted as a twisted sort of social police force.
Mainly they passed local and state laws which went against the 13th, 14th and 15th Amendments, forced freed slaves to live under Black Codes, and work in a system of sharecropping that closely resembled slavery.