Wikipedia is not a crystal ball and you cant create an article to be a collaborative research on a theory. I never even knew there was an article, but I'd imagine that it would be hard to source with reliable articles.

If anything you could source the fact that there was a conspiracy that triggered an event i.e. guy with gun, but over time, that particular incident wouldn't really even be considered notable.

I think the only way you could have it covered and not get removed is my going onto somebody's specific page and adding something that is one or two sentences, that they themselves said about it and that they were quoted saying in many reliable news sources.

They are living people, and the encyclopedia doesn't exist as a platform to slander people, so I can't imagine being able to add anything more than "X was mentioned in a conspiracy theory, said it wasn't true. Person with gun went to restaurant after reading about it."

If they never publicly acknowledged the theory, you really can;t use it in a quote.

I have recall reading a biography of a politician that many years ago said he saw a UFO, and there is definitely a sentence about it in there with many man many sources.

Anyways, I don't think its appropriate to add in a liviing biography unless they have actually been charged with a crime, and its sometimes is even hard to get that added, especially if they havent been convicted of the crime, just charged.