Kennedy defended the article insisting no one has shown “one mistake” he made in the article
That’s not how fact works. can make some statement but that statement doesn’t pass into “fact” just because no one has yet to provide a list of where got it wrong.
If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense.
The burden of proof lies with the person making the outrageous claims - in this case with conspiracy theorist RFK Jr.
The burden of proof is not on other people to disprove whatever outrageous conspiracies a conspiracy nut job comes up with.