Hubert Wayne Cash, 65, a Navy veteran and retired phone company worker, spent an hour at his home Tuesday explaining why he allowed the recent erection of a giant Confederate battle flag in his wooded back yard north of Fredericksburg overlooking busy Interstate 95.

“I’ve got 50 ancestors who fought in the Civil War,” Cash said. “I honor their heritage.”

Lights are being installed so the provocative banner will be visible at night. Cash said he leased the ground at a token price to the Virginia Flaggers, who share his sympathies for Southern secession, so the flag can fly “for at least 100 years.”

The gray-bearded Cash was gracious and thoughtful. I applaud his willingness to answer skeptical questions from an incorrigibly pro-Yankee news columnist.

But I still think Cash and his allies are wrong to display the flag. It’s the principal emblem today of a hateful cause — the protection of slavery — from which it cannot be divorced.

A Confederate Battle Flag is seen on Interstate 95 between Quantico and Fredricksburg in Virginia in July 2014. (Yue Wu/The Washington Post)

Germans don’t use Nazi swastika flags to honor their dead from World War II. The same logic applies to the Confederacy, even if the Nazis’ sins were worse than those of Jefferson Davis and company.

Of course, the United States can’t ban the Rebel banner outright, as German law prohibits the display of swastikas. The First Amendment protects freedom of speech.

But the public can and should try to shame the Confederacy fan club into scrapping the emblem of a wicked purpose and leaving it to be displayed only in museums and history books.

There are plenty of other ways to commemorate one’s Rebel ancestors. What about plaques, flowers or the Virginia state flag? The Confederacy was big on states’ rights.

The flag on Cash’s property in southern Stafford County drew objections from the local NAACP and several people whom I interviewed at a nearby convenience store.

“I don’t think it’s a good idea,” Wayne Samuel, 61, said. “It could be encouraging hatred.”

Vickie Browning, 51, said: “I think it needs to be replaced by an American flag. . . . [The Civil War] is done. It’s over. They need to let it go.”

It isn’t the only Rebel banner to arouse controversy recently. Washington and Lee University last month removed Confederate flags from Lee Chapel — where the Rebels’ most famous general, Robert E. Lee, is buried — following protests from African American students.

Here’s my main complaint about the flaggers, which Cash did little to dispel: Like many in the “Southern heritage” movement, they aren’t just committed to honoring individual Rebel soldiers. They insist also on trying to whitewash the Confederacy by saying the Civil War was about something other than slavery.

This was evident in the Virginia Flaggers’ announcement of the May 31 erection of the Stafford County flag.

The group said on its Web site that the Confederates took up arms for the sake of the “preservation of liberty and freedom guaranteed by our forefathers and embodied in the US Constitution of 1788.”

It’s a glaring contradiction to say the Confederacy fought for “liberty and freedom,” given that the driving force behind secession was opposition to the election of Abraham Lincoln as president. He philosophically opposed slavery and wanted to block its expansion.

Note also the flaggers’ enthusiasm for the U.S. Constitution of 1788, which formally counted slaves as three-fifths of a person.

Cash endorsed this interpretation of history. He said the Confederates were motivated principally by opposition to taxation, and he stressed that he bore no personal racial animus.

“We’re not sitting around like a bunch of yokels thinking slavery was a good thing,” Cash, speaking in his first news media interview, said.

Adding that none of his Confederate ancestors owned slaves, he said, “You think they fought for someone else’s slaves?”

Well, yes. His forebears may not have intended it, but that was the result.

Consider South Carolina, which started the fighting by bombarding Fort Sumter. Its formal explanation for seceding focused overwhelmingly on complaints arising from what it called “the increasing hostility on the part of the non-slaveholding States to the Institution of Slavery.”

Or listen to prominent Civil War historian James McPherson. His Pulitzer Prize-winning book, “Battle Cry of Freedom,” says, “The upper South, like the lower, went to war to defend the freedom of white men to own slaves and to take them into the territories as they saw fit.”

That’s how history happened. We should discourage the misguided from using an offensive flag to pretend otherwise.

I discuss local issues Friday at 8:50 a.m. on WAMU (88.5 FM). For previous columns, go to washingtonpost.com/mccartney.