Supporters of displaying the Confederate battle flag in public places like South Carolina's statehouse often argue that it's about "heritage, not hate." But as political scientists Spencer Piston and Logan Strother write for the Washington Post's Monkey Cage blog, there is actual data measuring how Confederate flag supporters and opponents each feel about the South and its history. And, frankly, it doesn't look good for the "heritage, not hate" argument.

In 2004, the Survey Research Laboratory at Georgia State University surveyed 522 white Georgia residents about a version of the Georgia state flag that included the Confederate battle flag. (This was the official Georgia state flag until 2001; in 2004, there was a referendum in which Georgia voters could vote for it to be reinstated.) And they found Confederate flag supporters didn't know much about the actual Confederacy.

The survey asked three questions about the Civil War — identifying Union general William Tecumseh Sherman, who famously burned his way through the state, and naming any two Civil War battles. A third of people who got all three questions right supported keeping the Confederate battle flag on the Georgia flag. Three quarters of those who got none of them right did. (This wasn't just because less-educated Georgians were more likely to support the Confederate flag, either; the researchers controlled for education level and income, and there was still a correlation between liking the Confederate flag more and knowing less about the war.)

So, how about the hate side of the equation? More bad news for the "heritage, not hate" slogan. Confederate flag supporters were much more likely to oppose interracial dating, and to believe that African Americans aren't discriminated against for jobs, than opponents were.

Supporters of the Confederate flag were more likely to say that they "felt close to other Southerners" — which is some evidence for the heritage side of the equation. But to make sure that feeling "close to other Southerners" wasn't a euphemism for disliking black Southerners, the researchers took a second look controlling for anti-black attitudes. When racism was accounted for, someone who supported the Confederate battle flag wasn't any more likely to say he felt close to other Southerners than someone who opposed it.

As the researchers point out in the Post, this is an 11-year-old survey here. It may not reflect the debate in 2015. But then again, Confederate flag supporters were saying it was about "heritage, not hate" then too.

CORRECTION: This article originally said that the Georgia state flag incorporating the Confederate battle flag was being used in 2004. It had been replaced in 2001. In 2004, there was a referendum that would have reinstated it.

Watch: Bree Newsome takes down the South Carolina Confederate flag