Strangely enough, years later his attorney's argued that he was framed. Even RFK's son, Robert F. Kennedy Jr., believes that Sirhan Sirhan was framed and did not actually conspire to kill RFK. He actually wants Sirhan Sirhan released [0].
[0] https://www.sfchronicle.com/opinion/openforum/article/Robert... [1] https://justiceforrfk.com/index.html
Nobody argues that Sirhan conspired to kill RFK and shot a revolver at him, and very few people question the leadup to that attempt.
Point taken, however, that RFK's assassination is not an unquestioned case of a single deranged individual.
Now one of the most prominent and vocal anti-vaxxers.