They certainly thought, campaigned, gave speeches and wrote that they were. What evidence do you have that they didn't?

For example, in his widely reported and printed cornerstone speech declaring the independence of the confederacy Alexander H. Stephens, the Confederate vice president and one of the most perceptive and brightest men in the Confederate government declared that, “Our new government is founded upon . . . its foundations are laid, its corner-stone rests, upon the great truth that the negro is not equal to the white man; that slavery – subordination to the superior race – is his natural and normal condition.” Stephens denounced the northern claims (which he incorrectly attributed to Thomas Jefferson) that the “enslavement of the African was in violation of the laws of nature; that it was wrong in principle, socially, morally, and politically.” He unabashedly asserted: “Our new government is founded upon exactly the opposite idea.” Stephens argued that it was “insanity” to believe “that the negro is equal” or “that slavery was wrong.” He proudly predicted that the Confederate Constitution “has put at rest, forever, all the agitating questions relating to our peculiar institution-African slavery as it exists amongst us-the proper status of the negro in our form of civilization.”