"maintaining and protecting the institution known as negro slavery - the servitude of the African to the white race within her limits"
As opposed to most wars, where history was written by the victors, in the US Civil War was mostly written about by the losers. They immediately went about reinventing the war in order to ease their conscience. I mean, the South deliberate started the war to defend an absolutely evil act (slavery), and in the ensuing conflict brought utter ruin on their society. The North was complicit in this rewriting because their main interest was in reintegration and reunification of the country.
Unfortunately, fast forward 100+ years, and now we have people talking about state's rights, and not about slavery. Counterrevisionism, in this case, is more than justified.
As far as Southern states were concerned, slavery was perfectly legal, culturally acceptable and morally correct, so they wouldn't see a need to mince words. It's only in the modern context of historical revisionism that such whitewashing is necessary.