Short answers, pulled from the story.
Virginian journalist Edward A. Pollard wrote The Lost Cause: A New Southern History of the War of the Confederates, which first appeared as a title in 1866. His publisher requested the change from his original title History of the War to ensure better sales.
The central argument denied that slavery was the primary cause of the Civil War and claimed it would have naturally perished over time. This narrative ignored constitutions published by seceding states and speeches like CSA Vice President Alexander Stephens' Cornerstone Speech which declared slavery the cornerstone of the Confederacy.
Frederick Douglass wrote that forgetting the difference between those fighting for slavery and those fighting for liberty would be a mistake in 1870. He opposed Confederate memorials and called them monuments of folly that perpetuated a wicked rebellion.
Mildred Lewis Rutherford served as national historian from 1911 to 1916 and advocated excluding narratives about slavery horrors from textbooks. Her 1919 publication A Measuring Rod to Test Textbooks set guidelines for schools to omit secession causes tied to slavery.
Black clubwomen prevented the erection of such monuments despite Senate support for bill S.4119 passed on the 28th of February 1923. Mary Church Terrell led campaigns against these statues arguing they erased slavery's horrors.