You are referring to the report mentioned in this article: https://www.logically.ai/factchecks/library/a341c089

As the article explains, the term conspiracy theorist predates this report by at least 100 years; in fact it had popular utility in the early 1900's when the Protocols of the Elders of Zion was released.

The CIA memo you are referring to was publicly released in 1998, and you can read in its entirety here: "Countering Criticism of the Warren Report" (1967)
https://conspiracy-theories.eu/countering-criticism-of-the-warren-report-psych-1967/

Interestingly, the term "conspiracy theorist" is only mentioned once, in plural form.

This is the problem with making your argument based on "I remember reading some time ago" or "my friend told me" or "I saw on Facebook"... lazy conspiracy theorists take a kernel of truth (the fact the memo exists) and blow it up out of proportion, often without having read it themselves. It is unfortunate because it detracts from the conspiracy theorists who ask real questions which everybody should be trying to answer.

I always was frustrated wanting to talk seriously about these issues with conspiracy theorists who just haven't done the research. I remember referring to the 9/11 report when this guy starts ranting about "why would I read that?? it's all lies anyway." But of course, if you haven't read it, how would you know? People reject the "mainstream" story right on the face of it, because they are unwilling to be open to what's in it - in other words, they've already made up their mind and they do not require any more information, other than "supporting information" which their confirmation bias will allow.

I actually have tremendous respect for conspiracy theorists who come up with plausible, researched, reasoned theories. Thompson's work is fantastic and from my brief exposure to Mr. Donahue here he would appear to be immersed in fact-based arguments.

The reality is that conspiracies DO happen - and we KNOW this because of proven conspiracies such as Watergate. The Mafia itself was one of the most vast conspiracies that ever existed; the fact that it did with thousands of members and it took the government 30 years to admit its' existence is simply incredible. So, if we know that conspiracies do actually happen, then there is an important role to play in asking tough questions. Asking uninformed questions however based on half-truths and misinformation simply muddies the water and gets everybody nowhere.