It’s been 150 years since the Civil War ended, but the Confederacy never really went away. It just got reabsorbed, more or less intact, back into the United States. And today the fight is still going on. Indeed, in some ways—ironically thanks to social media—the nation is more segregated and disunited than ever.

The last battle of the Civil War ended at Palmito Ranch, Texas, on May 13, 1865, and yet many more battles have been fought since then. Reconstruction was marked by racial terrorism, the emergence of the Ku Klux Klan and the return of former Confederates to government leadership in the South, where they set about writing laws to disenfranchise blacks and keep them a few pegs down the societal ladder, if not quite in the chains they wore as slaves. Even when Jim Crow segregation laws were eliminated by the U.S. Supreme Court and the Civil Rights movement in the past half century, the spirit of the Confederacy endured in the hearts and homes of many in the South.

Among them, it appears, was Dylann Roof, who before he allegedly murdered nine people in a black church in Charleston, South Carolina, on Wednesday reportedly posted a "manifesto" in which he poured out vicious racist sentiments, declared that he hated the American flag and wrote that "segregation was not a bad thing... Segregation did not exist to hold back negroes. It existed to protect us from them." Posted on the site are pictures of Roof with a Confederate flag and visiting the graves of Confederate soldiers.

Such sympathies are not limited to the deranged. The Confederate battle flag remains a politically and racially charged symbol of the region’s past. It appears on T-shirts, bumper stickers and in the front yards of plenty of houses around the South. It’s flown on the capitol grounds in Columbia, South Carolina, where it flew at full-staff all day Thursday despite the atrocity at the Emanuel African Methodist Episcopal Church.The reasons the flag stayed at full-staff while the state and U.S. flags were lowered to half-staff are rife with politics and history, but that doesn’t change the fact it added insult to injury for many residents.

White Southerners who celebrate the Confederate battle flag nearly always link it to their ancestors and geography, not the cause of slavery and racial segregation. They sincerely believe it’s all about heritage, maybe mixed with a touch of rebellion and flipping the bird to the powers that be. Only last week, in another one of these post-Civil War battles, the Supreme Court had to weigh in on the issue yet again, ruling that Texas had the right to ban the image of the Confederate flag from its license plates.

The flag’s connotations place a special responsibility on Southerners who want to celebrate their ancestral heritage but not its connection to race. They have an obligation to call out white supremacists who may otherwise find a tolerant, even friendly, place in the former Confederate states. The problem is that too many white Southerners don’t—or won’t—understand why the battle flag and other symbols of the Confederacy might be hurtful to others.

“It’s definitely a symbol of white supremacy, and also a symbol of their heritage,” said Brandon Hicks, a recent graduate of Washington and Lee University School of Law. “Their ancestors were likely white supremacists. They didn’t want equality for African-Americans. But we don’t celebrate bad aspects of our heritage. If it wasn’t a symbol of white supremacy, why would they carry it when they lynched people? Why would they carry it when trying to close schools? We’re not talking about slavery. We’re talking about things that happened in the ‘60s.”

Many are simply in denial, says Heidi Beirich, director of the intelligence project for the Southern Poverty Law Center. There is a large contingent of people within groups like the Sons of Confederate Veterans who join because they’re interested in heritage and history. But despite the group’s insistence that the South’s primary motivation in the war was “preservation of liberty and freedom,” the fact is that its members are defending a government that was built to protect slavery, she says. According to Beirich, the Sons of Confederate Veterans spent the mid-‘00s in a pitched battle between members who wanted to focus on heritage and those who were more interested in racial politics, ultimately resulting in the expulsion of 400 or more anti-racists from the group.

One of them was Gilbert Jones, who penned an op-ed for North Carolina's Greensboro News & Record in January headlined, “It’s time to furl Confederate flag.” “The Sons and its leadership are in psychological denial about the battle flag’s symbolism,” Jones wrote. “It is time for them to come clean and admit that many of our fathers and grandfathers, even some of their current members, used the battle flag for the wrong purpose during the time of the civil rights struggle. … The meaning that it held for Confederate soldiers in 1865 is not the meaning it holds today.”

Is it any wonder that a deluded Dylann Roof reportedly thought he could start a “race war” by gunning down black people in a church?

The flying of the Confederate flag at full-staff in Charleston, even after the massacre, was hardly an isolated act. Last year, a group of black law students at Washington and Lee University requested Confederate flags be removed from the campus chapel and that Confederate reenactors be banned from campus during Virginia’s Lee-Jackson holiday, which celebrates Southern generals Lee and Thomas “Stonewall” Jackson.

University administrators complied, writing a letter that acknowledged the flag's role in slavery and recognized Martin Luther King Day, despite pitched opposition from the regional chapter of the Sons of Confederate Veterans and a group known as the Virginia Flaggers, which has placed battle flags along many of the state’s roads. In addition to mounting huge marches on Lee-Jackson Day, at least two protesters waved battle flags at the university on a weekly basis. Hicks, who was one of the students who raised the issue, said he walked past them regularly on his way to classes.

“It’s all a continuum,” says Hicks, who links the Charleston shooting to what he saw at Washington and Lee. "This man was raised in a state that refuses to stop offending its taxpayers, a large percentage of its population. It has a symbol of slavery flying from its state capitol. This man was raised in the state. He is a product of its education, the government of South Carolina, which every day says blacks don’t matter, black feelings don’t matter.”

A number of former Confederate states—Alabama, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee and Virginia—still offer the Confederate battle flag on a government-sanctioned license plate. Roof, the Charleston shooter, had such a license plate on his own car. Despite last week’s Supreme Court ruling that states may reject license plates bearing the image of the flag, officials in Alabama already have said they have no plans to discontinue the plate. It’s unclear how other states will respond to the ruling.

These skirmishes take place within a societal context in which individuals have increasingly retreated from public debates to the confines of their own homes, often in segregated communities and with information streams that can all too easily be tweaked to keep out discomforting or challenging viewpoints.

Many U.S. cities remain racially segregated. It’s true around the country, and especially in the South, where government-sanctioned segregation and urban renewal have divided racial populations by neighborhood. The so-called Big Sort, with people moving to politically like-minded regions and communities, and the proliferation of ideologically oriented mainstream and social media streams has amplified the effects of physical segregation. Someone comes across an opinion they don’t want to see or hear? They change the channel on television, and hide, block or unfriend the source on social media.

Thus we have the spectacle of a country that, aided by modern technology, is less united rather than more united. Individuals get caught in bubbles that reinforce, not challenge, their beliefs. Understanding and empathizing with those of different races becomes even more difficult when one is not interacting with them on a regular basis. Very few people believe they’re racist, but stereotypes about “thugs” and particular neighborhoods become entrenched as conventional wisdom. This becomes a “soft” racism that pervades thinking and occasionally erupts into ugly online rhetoric.

When Jesse Matthew was arrested and linked in the homicides of two white college students in central Virginia, comment threads at Virginia media outlets sounded like something from the late 19th century. Some commenters essentially called for his lynching. As Sarah Kendzior observed, the conversation on race is happening, and it’s angry and uncomfortable. It plays out every day in comments on Facebook and below stories at hundreds of broadcast and print news sites around the South and the U.S. more generally.

In the South, neighborhood and cultural segregation, paired with the presence of emotionally charged symbols such as the Confederate battle flag, provides cover for those who still hold racist beliefs in white supremacy. It’s what encouraged neo-Nazis like Bill White, who took up residence and published his white power magazine in Roanoke, Virginia, before eventually going to prison for threatening a juror in a federal case.

Too many people are still willing to ignore people like White—to let it go when someone makes a racist joke. Dave “Mudcat” Saunders, a Roanoke political consultant once photographed with his battle flag quilt, said that’s starting to change.

“You don’t hear the n-word like you used to,” Saunders said. “When I used to hear someone say it, I’d slough it off, but now, if someone says it, I call them on it.”

If that’s truly happening, it’s still not happening often enough to discourage white supremacists like Roof or White. The Southern Poverty Law Center’s Beirich says the cultural bubbles that people build represent an obstacle toward addressing the issue of hate crimes and white supremacy movements.

“We’re becoming increasingly diverse, and if everyone retreats to their own corner with their own folks, that’s going to become more of a problem in the future,” Beirich said. “People treat the Bill Whites of the world like that’s the crazy uncle up in the attic.”

The Charleston shooting this week came not long after Democratic presidential candidates and surrogates spoke to South Carolina Democrats, including state Sen. Clementa Pinckney, a pastor and victim of the shooting. Saunders was there speaking as a surrogate for former U.S. Sen. Jim Webb, who is considering a presidential campaign.

“I talked to them about the post-racial society that Jim Webb believes in,” Saunders said. “The damn deal is this: The post-racial society should begin in the South, especially in South Carolina where campaign wedge politics were introduced in 1980. The one thing that we have in common is a strong affection for the Almighty, our faith. We are a faithful people, native Southerners. I don’t put God into politics—I don’t believe in doing it—but in this case I will. Faith is the one thing that could bring us all together. I think the bombing of the four little girls in Birmingham, Alabama, opened a bunch of white eyes in the ‘60s. Hopefully 50 years later, this will open up more white eyes. This kid was trying to start a race war. Hopefully it can do the opposite.”

The white supremacists who actively work to maintain/resurrect the Confederacy are a tiny fraction of white Southerners—but geographic and cultural segregation and pride in “heritage” while ignoring the Confederate battle flag’s nasty history helps provides them cover and a cozy atmosphere in which to pursue their mission. Thus the Confederacy lives on.