Because, at the end of the day, for many of the neo-Confederates the suffering of human beings reduced to slavery is a small price to pay for hoop skirts, cotilions and mint julips.
They've gotten smarter over the last generation or so, these apologists for the proto-fascist system in the Old South. They've shed the language of the 1960's segregationists and Klan members and replaced it with their "gracious civilization" and "Dixie liberty" pap.
The neo-confederate movement's chef ideologues realize if they could control how people recall the past, they will control how people approach the present and the future.
Whenever the promoters of the neo-confederate agenda attempt to pervert, twist & alter the real history of the Old South, this deceptive element will always be unmasked by those well aware of their real goals.