The potential for military coup had never been a problem in the U.S. military for the reason of well-established civilian control of the military as well. The closest thing to a real problem having been MacArthur's insubordination to Truman. That problem arose in part through the old system where senior generals kept their positions forever in a hard-wired seniority system. Many of the problems of that antiquated system were dealt with by the Goldwater-Nichols act http://en.wikipedia.org/wiki/Goldwater-Nichols_Act
Gerald C. MacGuire was a $100 a week bond salesman for Murphy & Company. Smedley Butler was retired military and the one who blew the whistle on the whole affair, which most contemporaries and historians dismiss as a cocktail putsch, i.e. wild talk at a cocktail party. I don't think there's a way to spin any military involvement in an attempted, or even contemplated coup in this case.
