John Brown was tried by Virginia and found guilty of treason against the Commonwealth of Virginia, whatever that means. He was not tried in federal court and could not be charged with or found guilty of treason against the United States. Here is a website with details.
Herbert Hans Haupt was convicted of sabotage and executed for it. What you, with your DiLorenzo-like devotion to truth and details, have done is confuse his case with that of his parents. Haupt's parents, Hans and Erna Haupt, along with his aunt and uncle and two family friends, were arrested in Chicago shortly after Haupt was caught. They were tried for treason for conspiring to help Herbert Haupt. They were convicted, but sentenced to life in prison.
Sorry, old sport, but Walt is right and you are wrong...again.
What is not to understand? Lee would have been guilty of the same had he accepted a Union commission.