This claim is made in the amazon.com description of the book I Was a Teenage JFK Conspiracy Freak by Fred Litwin. I presume Fred Litwin wrote the amazon description for his own book so, if i'm correct, this allegation is coming from him. The book description goes as follows:
I Was a Teenage JFK Conspiracy Freak demonstrates how the left and right have used the JFK assassination to drive home myths about power in America. There is also the persecution of a gay man prosecuted for conspiring to kill Kennedy, the ugly story of Oliver Stone’s homophobic film JFK, an exposé of conspiracy nonsense on the Canadian Broadcasting Corporation, a look at how the Soviets tried to influence American public opinion that CIA was behind the murder, and the incredible secret why some JFK assassination documents must remain locked up. And a whole lot more.