The Cleveland Plain Dealer discredited Junior's theory in a column written by Ted Diadiun on Sunday, June 18, 2006, and The Plain Dealer is a lib rag! I don't know how to attach an article (sorry), but if you go to their website, you can read the article.
Salon also ran a piece that totally debunks RFK Jr's article:
http://www.salon.com/news/feature/2006/06/03/kennedy/index.html