Between 1967 and 1973, Mr. Sletson served as the executive director of the Philadelphia chapter of the National Committee for a Sane Nuclear Policy. At various times, the chapter honored Joan Baez and Dr. Benjamin Spock, his son said.
Mr. Sletson served in the Army in occupied Germany late in World War II. He covered the Nuremberg trials for the Stars and Stripes. The experience helped forge his antiwar views.
By 1967, he had developed objections to American participation in the Vietnam War.
"It was an intervention into a civil war," Mr. Sletson told a reporter. "I didn't think we belonged there."
A fund-raising and public-relations consultant both here and after relocating to State College, Pa., in the 1990s, Mr. Sletson joined the State College Peace Center and spoke out against the presence of U.S. soldiers in Iraq.
"When people speak and the issue is war, they deserve to be heard," he told the State College Centre Daily Times in 2008. "It's up to the American people to bring the troops home. Not Gen. [David] Petraeus. Not President Bush. The American people. That's what happened in the Vietnam War."
Born in the Bronx during the Depression, he played street football using a ball made of tightly rolled newspapers tied with string, he told family.
By age 30, he was a Fuller Brush salesman, married to the former Joele Van Zeen, and the father of two boys. The couple soon divorced.
He lived in West Philadelphia and the Fairmount section of the city.
In 1968, he was Sen. Eugene J. McCarthy's Pennsylvania presidential campaign manager. Four years later, he worked for Sen. George S. McGovern's campaign for president.
In the 1980s, he founded Funds for Progress, a consulting firm that helped liberal nonprofits raise money.
In addition to his son and former wife, he is survived by another son, Jay; a grandson; his companion, Darlene McMinn; and nieces and nephews.
A memorial service will be at 1 p.m. Saturday, April 13, at the Unitarian Universalist Fellowship of Centre County, 780 Waupelani Extension, State College.
Condolences to the family may be offered at www.heintzelmanfuneralhome.com.
Contact Bonnie L. Cook at 215-854-2611 or firstname.lastname@example.org.