Forrest Sorrels was the Special Agent in Charge of the Dallas office of the Secret Service when JFK was assassinated.
He was riding in the lead car immediately in front of JFK's limo. Sorrels was adamant in his belief that some of the shots were fired from the direction of the grassy knoll.
Several other Secret Service agents in the area that day believed that shots were fired from the grassy knoll, and that there was a conspiracy involved.
I suppose it's just a "coincidence" that Jack Ruby, the man who shot Oswald, was involved in gun-running to the communist Castro regime for several years prior to the assassination.
One has to be pretty gullible to believe that Ruby killed Oswald out of "patriotism". Especially considering that Ruby was born and raised in Eastern Europe and was known to have socialist sympathies. He immigrated to the U.S., where he just "happened" to run a night club with known underworld connections.
Just because some conspiracy theories aren't realistic, doesn't mean they're all bunk. Examples of very real major conspiracies would be the Communist and Nazi conspiracies, the Thuggee cult in India, and La Cosa Nostra (the Mafia).