According to the people behind another PBS show, History Detectives (Cowan just happens to be the host), that conclusion started an uproar that set sleuths on a trail into the past, and to a meeting with University of Pennsylvania historian Mary Frances Berry, the results of which are revealed Tuesday on that show at 8 p.m. on WHYY TV12.
Mississippians Chandler Battaile and Bobbie Chandler, descendants of the men in the picture, recount their families' histories, which include stories that the black man, Silas Chandler, fought alongside the white man, Andrew Chandler, and saved his life. Another tale has the white family giving land to a group of freed slaves after the war.
Bobbie Chandler says he has no qualms about the family histories, but he implies that many of his relatives are suspicious of stories that paint the slave owners as loving and benign toward the people who were their property.
The descendants don't discuss a 1994 ceremony, the first such one for an African American in Mississippi, when the Sons of Confederate Veterans and the United Daughters of the Confederacy held a dedication at Silas Chandler's grave. They hailed him as "a black Confederate soldier," and placed a marker in the form of a Southern Cross of Honor (also known as the Iron Cross of Honor) on his grave.
Some of his descendants attended and participated in the ceremony, but others signed a petition objecting to it and the placement of the Iron Cross and a Confederate flag on Chandler's grave.
The marker and flag were misguided, said Berry, who is the Geraldine R. Segal professor of American social thought and professor of history at Penn. Present-day groups may seek to downplay slavery and race as a cause of the war and to upgrade the position of blacks in the Confederate Army, but the Confederate States of America was built on the principle that Negroes were an inferior race.
"The Confederacy, as a so-called nation, always prohibited the use of slaves as soldiers, until the last months of the war," Berry said, when the pool of white would-be soldiers was depleted, and desperation was the order of the day.
That is not to say that many African Americans did not serve their masters individually in the war as valets, porters, or cooks, or that slaves and their masters did not have human relationships.
"Princeton at the time was a great hotbed of Southern gentlemen," Berry said. "Slave masters took a slave with them to college. You might have thought they were friends.
"If you look at the tintype, the first thing you see is there's a relationship," said Berry. "But none of what's in the story changes the whole narrative of the Civil War. About 200,000 blacks fought for the Union. None was accepted by the Confederate government."
Through an old ledger and a fancy stock certificate, History Detectives also will examine the lives of American Indians in the early movie business, and the development of a little farm town named Harlem, north of New York City.
The stuff on the Roadshow, usually PBS's highest-rated series, is fascinating, and it's always fun to find out what it's worth, but the real history that the Detectives unearths provides more provocative fare.
8 p.m. Tuesday on WHYY TV12
Contact television critic Jonathan Storm at 215-854-5618 or firstname.lastname@example.org. Pittsburgh Post-Gazette reporter Frank Reeves contributed to this article.