America is rooted in a Christian tradition, therefore all political movements that sprung from it also liberally borrowed from this tradition (including, paradoxically, movements that explicitly rejected Christianity). This includes the white supremacists in the South, but it would be dishonest or ignorant to ignore religious influence on abolitionism and the civil rights movement. In Douglass' most famous speech he speaks at length of how Christianity represents both a corrupt institution of slave power and (to him) the methods of destroying that power simultaneously.
“I love the pure, peaceable, and impartial Christianity of Christ: I therefore hate the corrupt, slaveholding, women-whipping, cradle-plundering, partial and hypocritical Christianity of this land. Indeed, I can see no reason, but the most deceitful one, for calling the religion of this land Christianity. I look upon it as the climax of all misnomers, the boldest of all frauds, and the grossest of all libels.“ - Frederick Douglass
