Today is the sesquicentennial Juneteenth, marking 150 years of emancipation. Today, the battle flag of the Confederacy still adorns the grounds of the South Carolina state capitol, just as it adorned the license plate of Dylann Storm Roof’s car. South Carolina fought under the Confederate banner for years; today it fights over that banner. Wednesday’s killings have renewed the longstanding demand that it be taken down for good. According to some reports, that might not be possible under current state law. If those reports are accurate, then the law must be changed.

The presence of the Confederate flag throughout the South is sometimes defended by vague rhetoric about remembering the past and the limp assertion that the flag isn’t really about racism. (With the implicit premise that its display would be unobjectionable if it were merely a symbol of treason.) This defense is historically illiterate. The Confederate battle flag was relatively dormant after 1865; its popularity and visibility were revived as part of Civil Rights-era racist agitation. Georgia led the revival movement, adding the battle flag to its state flag in 1956 as a defiant response to Brown v. Board of Education. Other states, including South Carolina (1962) and Alabama (1963), followed suit for the same reason—to oppose racial integration and affirm white supremacy. The states intentionally resuscitated a familiar symbol of the Slave Power, one that—as a standard carried into battle—also suggested their willingness to defend with violence what that power stood for.

Ever since, the flag’s apologists have been tenaciously defending its continued display, aided above all by ignorance and indifference. After its mid 20th-century resurrection, the flag flew over the South Carolina statehouse until 2000, when it was moved in a compromise to a less prominent area on the capitol grounds. A Gallup poll at the time found that 46 percent of Americans approved of Southern states flying the flag—a decline from 55 percent in 1992. The flag remained a popular enough cause among South Carolina conservatives that in 2002, the state’s Republican attorney general, a gubernatorial hopeful, sued the NAACP for organizing demonstrations at the state’s rest stops against its continued display. (The lawsuit was later dropped.) A more recent poll, taken this year, found that 50 percent of South Carolinians support the continued display of the flag on capitol grounds, while 40 oppose it. 71 percent of the state’s Republicans are in favor.

Research seeking more detail on these supporters is informative, if unsurprising. A 2006 study, attempting to map opinion on the flag beyond just white Southerners (whose attitudes are the subject of most surveys), found that region and race—not just racial attitudes—also influence feelings about the flag. “Southern whites,” the researchers reported, “have the greatest support for the flag followed by nonsouthern whites, nonsouthern blacks, and southern blacks.” A 2010 study by a team of psychologists went further, investigating the effect of the flag. The study’s authors found not only that “participants primed with the Confederate flag reported less willingness to vote for Obama than those primed with a neutral symbol,” but that exposure to the Confederate flag also negatively influenced participants’ evaluations of a hypothetical black man. The flag itself seems to call up negative racial stereotypes about African Americans. Crucially, the authors discovered that the flag’s impact “was not predicted by individuals’ own racial attitudes”—meaning that it didn’t so much awaken racism in prejudiced participants as it summoned up negative racial stereotypes “among high and low prejudice participants” alike.

That’s a harrowing finding. One imagines it would bring a sickening smile to the faces of John Calhoun, Jefferson Davis, and Alexander Stephens—the latter of whom infamously declared that the Confederacy’s “foundations are laid, its cornerstone rests, upon the great truth that the negro is not equal to the white man.” The Confederacy went to war and nearly destroyed the Union for that idea, and they did so under a battle flag whose meaning Dylann Roof understood perfectly well. It’s Juneteenth. Let’s commemorate the day fittingly. Let’s stop flying their flag.