Today's Neo Nazis also Drink Milk...
Hitler was a Teetotaler
you appear to suffer from False Equivalency...
FYI This was Never the Flag of the CSA... it is the Battle Flag of Northern Virginia... Like most 'symbols of the south' it was retired when the war ended...
It wasn't until the 20th Century with 50th/100th Anniversary dates of Civil War Events were being noted that saw the Flag taken out of Mothballs... For much of the 60s, 70s and 80s the Flag was Nothing more than pop Culture shorthand for 'The South', with no more meaning to the Flyer, or the Viewer than "I'm from There" (or "my agent told me you'd buy more content if you think I am")
It was these anniversaries and the Rise of the Civil rights fights that say 'the Klan' start to use them, Not because of what they Meant 100 years ago, but because they were easy to find thanks to the 'pop culture'