On Monday, South Carolina Governor Nikki Haley said the Confederate flag should be removed from the Statehouse grounds.

Once again, South Carolina has sunk back into the quagmire of its old quarrel about "that flag," which is, of course, really its older quarrel about the meaning of the Civil War.

Just hours after the shooting of nine black worshippers at the historic "Mother" Emanuel African Methodist Episcopal Church in Charleston on Wednesday evening, there were fresh calls to "take it down!"

The president of the NAACP, Cornell Brooks, standing in sweltering heat on the sidewalk outside his Charleston office roared that the flag was "an emblem of hate … a tool of hate … an inspiration to violence."

You know the flag he means: the blue "X" with 13 white stars on a square red background. It is known as the Southern Cross; officially it is the Confederate Battle Flag.

A protester holds a sign asking for the confederate battle flag that flies at the South Carolina State House to be removed in Columbia, S.C. on June 20, 2015. (Jason Miczek/Reuters) Notoriously, it is also a symbol for hundreds of extremist groups across the southern United States, including the Ku Klux Klan.

Yet the flag flies proudly on the grounds of the state capitol in Columbia.

The offense is obvious. For African Americans and many others, the flag was the standard of those who fought to preserve what was known as their "peculiar institution" of slavery, and it continues to be a symbol of racist oppression today.

There should be no debate about that, but there is.

Defenders of both the war and the flag say the Civil War was fought to protect states' rights. But the pretense that what was really at stake in the Civil War was a noble constitutional principle about states' rights collapses under the weight of an ugly truth: The southern states fought to protect the right to own slaves.

We've been through all this before. Fifteen years ago, there were calls to remove the Confederate flag from the dome of the state legislature in Columbia where it had been raised decades earlier to mark the centennial of the Civil War. That ended in a compromise that saw the flag removed from the dome and installed near a Confederate soldier memorial at a main entrance to the state house.

But even that small concession was bitterly fought and hard-won.

A Civil War re-enactor holds the Confederate flag as he stands with other re-enactors during the annual Confederate Memorial Day Service in Winchester, Va. on June 6, 2015. (Jeff Taylor/The Winchester Star/Associated Press)

March to the capitol

Charleston's Mayor, Joe Riley, who spoke so eloquently about the tragedy in his city last week, walked with hundreds of others all the way from Charleston to the capitol in 2000 to demand something be done about the flag. It took him four days to get there and he wore a bullet-proof vest as he walked.

At about the same time, 116 scholars of history, mostly from South Carolina, felt compelled to sign a public statement telling South Carolinians that, yes, the Civil War was, in fact, fought over slavery.

Just 15 years ago.

Their letter quoted William Preston's ignoble rallying cry as he led the South Carolina delegation out of the 1860 Democratic National Convention on the eve of the Civil War: "Slavery is our King; slavery is our Truth; slavery is our Divine Right."

What could be clearer?

But obfuscating the issue has its own history, as was illustrated by George W. Bush when he arrived in South Carolina for a primary debate during the 2000 election, when the controversy about the flag was already churning hard.

A demonstrator holds a burned Confederate flag during an anti-flag rally at the South Carolina Statehouse on June 20, 2015, in Columbia, S.C. (Rainier Ehrhardt/Associated Press) Moderator Brian Williams asked Bush if the flag personally offends him.

Bush recognized the invitation to take a principled stand and glided right on past it.

"I don't believe it's the role of someone outside South Carolina, and someone running for president, to come into this state and tell the people of South Carolina what to do with their business when it comes to the flag."

That's worth remembering for those curious about the kind of political calculus that has protected a place of honor for the Confederate flag to this day.

The flag no longer flies from the state house dome, but its display in front of the legislature is both prominent and entrenched in law: It cannot be removed or even lowered except as prescribed by statute. So it falls to South Carolina legislators.

In the wake of last week's tragedy, they will be asked again to find the courage and the votes to overturn a law that has preserved a place of honour for the Confederate flag and to finally hoist it in the only place it truly belongs, a museum.