Conspiracy theories about assassinations seem harmless nonsense next to these nuts who believe the July 7 attacks in Britain, the Sandy Hook school shootings, the Orlando nightclub shooting, and other such scenes of mass carnage are put-ons by actors paid to undermine gun ownership rights or any such absolute garbage. No doubt even lunatic opinions are protected by freedom of speech but perhaps this sort of statement if made seriously should be declared a crime, as is holocaust denial in Germany. You can't just claim anything--there are such things as slander and libel.
That being said, I believe at the very least such a mass of mistakes and screwups occurred during and after John F. Kennedy's assassination as to make it look like a coverup, either of a conspiracy or of people trying to downplay their own blunders. I voted yes that Oswald shot Kennedy, as I believe he owned the gun, brought it to the building, fled the building immediately afterwards having somehow left his finger and palm prints all over the gun, was the only employee found to be missing when a head count was made right after the shooting, and he did kill the police officer with another weapon and resisted arrest. It's been demonstrated that the shooting could have been accomplished by a really expert marksman using Oswald's rifle, and why conspiracists would recruit a nut like Oswald (other than as the perfect fall guy) or equip him with one of the crappiest weapons available to accomplish such a major goal are great questions.
It's been said that JFK and his brother RFK's shootings were connected--that Bobby was going to get to the bottom of who was behind Jack's death and so was killed. Recently it's been said that Aristotle Onassis had hated Bobby for at least 15 years and put up the money to have him killed, that Onassis's own daughter knew the money could be traced to him but wanted to believe it went for something else, and when she died the whole investigation was dropped. RFK's shooting was by more than one gunman whether or not it was a conspiracy or simply more than one armed person in the room out to get him. (It's believed Sirhan went to get him but did not fire the fatal bullet, and a security guard who hated Kennedy took advantage of the situation. Many people in the room were filming or taking stills and some of the images have mysteriously disappeared.) The only person shot in the head who appeared dead at scene was a man named Paul Schrade (despite the movie Bobby, it wasn't Elijah Wood). Paul Schrade is in fact still alive and it's been well demonstrated that the person who shot him cannot also have shot Robert Kennedy--Sirhan Sirhan never got far out of the same position and the shots were fired from completely different positions. Also I believe they found more bullets than that gun held, and Sirhan never reloaded.