McPherson is known for his outspokenness on contemporary issues and for his activism, such as his work on behalf of the preservation of Civil War battlefields. As president in 1993–1994 of Protect Historic America, he lobbied against the construction of a Disney theme park near Manassas battlefield. He has also served on the boards of the Civil War Trust as well as the Association for the Preservation of Civil War Sites, a predecessor to the Civil War Trust. From 1990 to 1993, he sat on the Civil War Sites Advisory Commission.