The fact that you need to explain that sort of demonstrates that it isn't relevant to the use of the argument. Good arguments can come from poor sources.

Most people agree that shouting fire in a crowded theatre is the sort of speech which should be restricted, wherever the argument came from.

> Good arguments can come from poor sources.

All the more reason to not silence cranks and conspiracy theorists.

From John Stuart Mill's On Liberty:

> But the peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.

https://en.wikisource.org/wiki/On_Liberty/Chapter_2

"the dictum that truth always triumphs over persecution, is one of those pleasant falsehoods which men repeat after one another till they pass into commonplaces, but which all experience refutes. History teems with instances of truth put down by persecution. If not suppressed forever, it may be thrown back for centuries."

– John Stuart Mill, On Liberty https://www.utilitarianism.com/ol/two.html

That's what I would argue If I had a conspiracy in mind.