He was valedictorian of his high school class and graduated magna cum laude from Harvard University in 1980, majoring in psychology, and writing his honors thesis on the testing of gifted children.
Writing sometimes under his own name and at other times under the pseudonym "Kenneth W. Kirkpatrick", he authored or co-authored several articles in the NEGHS Register and also wrote for the New Hampshire Genealogical Record, Vermont Genealogist and The Island Magazine.
Marshall was especially pleased by the prospect of an Edward III descent through Katherine Deighton (Dudley's second wife), Dennis and Stradling, and after publication of an article in Foundations attempting to refute it, was strong in its defense.
They argued that gays must portray themselves in a positive way to straight America, and that the main aim of making homosexuality acceptable could be achieved by getting Americans "to think that it is just another thing, with a shrug of their shoulders".
[1] The pair developed their argument in the 1989 book After the Ball: How America Will Conquer Its Fear and Hatred of Gays in the '90s, which outlined a public relations strategy for the LGBT movement.