The National League of POW/MIA Families also believes there are likely no live soldiers, but reminds supporters that still plenty are left "unaccounted"—meaning the service members' remains or documents surrounding their death have never been given to the families.
According to the Pentagon's prisoner of war and missing personnel office, the number of unaccounted is about 1,600.
The Department of Defense continues to try to recover the remains of those 1,600 service members through an office called the Joint POW/MIA Accounting Command at Joint Base Pearl Harbor-Hickam. But the American Legion, a veterans service organization, worries that DOD will suspend those efforts if automatic budget cuts kick in as planned on March 1.
Those cuts are likely to most anger groups who believe live soldiers remain in Vietnam, and suggest a U.S. government cover up.
The National Alliance of Families, which split off from the league because of this view, believes that at least several dozen POWs are still alive in Southeast Asia. On its website, it condemns "decades of government lies and denials" about soldiers who could be alive.
Popular culture hasn't helped disabuse that notion. The 1985 cult film "Rambo: First Blood Part II" depicts a Vietnam war veteran who goes to Southeast Asia to find POWs still alive, while the U.S. government is portrayed in the film as attempting to sweep the issue under the rug.
Franklin, who wrote the book "M.I.A., or Mythmaking in America," says the POW/MIA flag pushes the Rambo fantasy too far.
"The myth about hundreds, or thousands, who maybe became slave laborers, or were killed, or tortured, it's all up there in the flag," he says.
The disagreement over the flag goes beyond the live prisoner question. Some former service members have questioned the prominence of the symbol for other reasons.
"There was a time when a number of us felt like we should get rid of the flag because it was being used politically to keep the Vietnam war going," says John Swensson, a Vietnam veteran and professor emeritus of English at the San Francisco-based De Anza College.
In 1999, fellow Vietnam veteran Michael Kelley published a passionate piece opposing the flag on a Vietnam War research portal Swensson runs at De Anza College. "The POW/MIA flag honors a very narrow segment of the veteran population and does that to the exclusion of much larger and equally deserving ... segments of that same population," wrote Kelley, who died in 2011.
Kelley submitted the piece to express his frustration as a member of the California Vietnam Veterans Memorial Committee, and what he called "a number of vigorous ... zealous attempts to include the POW Flag on our memorial."
In 2007, a veterans memorial in Newburgh, Ind., caused controversy when it similarly resisted flying a POW-MIA flag alongside an American one.
Today, the POW/MIA flag flies above both memorials—in large part due to the efforts of Vietnam veterans who don't agree with Kelley.
But at some government buildings, such as the U.S. Post Office in Georgetown, Washington D.C., employees say they can't remember having ever flown the POW/MIA flag.
To combat this, Vietnam veterans such as Nick Haupricht have dropped off the flags at government buildings in his home state of Ohio, according to independent veterans site Veteran News Now.
Willie Hager has similarly pushed the POW/MIA flag in his state of Florida, ever since he lost fellow soldier and friend Thomas Hart in Vietnam. According to Hager, a forensic test showed that the remains the U.S. government sent to Hart's family post-war did not belong to their son, but were dog bones, a story that could not be confirmed by U.S. News.
Efforts by Hager, who is a member of the anti-war group Veterans for Peace, helped lead to legislation in Florida mandating that the flag be displayed over the state capitol. The flag currently flies over state capitols in a number of states, and earlier this month a bill for flying the MIA/POW flag over the Utah state capitol unanimously passed a House committee there.