Why do you think some people, like those that chose to be members of the kkk, verbally or physically attacked african-americans?

The answer is mention below.

Explanation:

The purpose of the foundation of the Ku Klux Klan, by the former Confederates, was to establish an "invisible Empire in the South". They rejected the reconstruction plan and there were enough evidences of violence against the Blacks and Whites (especially “carpetbaggers” and “scalawags”). They carried an underground campaign against the Republican leaders in the south. One of the examples of Klan activities was in January 1871, 500 masked men attacked the Union county jail and lynched eight black prisoners.