"Right-wing outlets" have been criticizing Wikipedia off and on for probably most of Wikipedia's history, and the basis for this criticism is not hard to understand. Harrison (apparently "the author of The Editors, a novel inspired by Wikipedia.") comes across as not interested in examining the argument, only in uncharitably dismissing it.
Wikipedia's page on Charlie Kirk claims, and has claimed for years, that
> Kirk promotes the Cultural Marxism conspiracy theory, and has described universities as "islands of totalitarianism."
at the top of a section currently titled "Promotion of falsehoods and conspiracy theories". Since May 6 2021 (https://en.wikipedia.org/w/index.php?title=Charlie_Kirk&diff...) there has been such a "Promotion of conspiracy theories" section, and even before that there was considerable edit warring over attempts to describe him as a "conspiracy theorist" in the first paragraph of the lede. (It doesn't appear to have this currently, but I have seen it like that since the assassination.)
The second part is a personal opinion, and unrelated to the first part. Two of the sources listed relate to the first part. One of these is from "Varsity Online", an "independent student newspaper for the University of Cambridge", which claims:
> Charlie Kirk, who was due to speak at the Union debate, has spoken out against what he sees as the proliferation of ‘cultural Marxism’ on campuses, and claimed in December that the gilet-jaunes protests in France were a “middle class rebellion against cultural Marxism”...
There is no attempt in this article to elaborate on what they think Kirk meant by this, nor to determine what he did mean by it. Which is presumably why they have the second source, which is an academic paper which attempts to define the term and brand it a conspiracy theory. The problem is, the paper doesn't mention Kirk. Using a term is not sufficient to establish that someone is pushing a related conspiracy theory; talking about, for example, the JFK assassination does not establish belief in any of the related conspiracy theories. Someone can easily hear a term like this and think it an accurate description, without having any idea about the conspiracy theory tied to it.
This sort of thing should be considered a blatant violation of WP:SYNTH and WP:BLP, and in my experience Wikipedia editors put immense effort into doing this sort of thing for prominent right-wingers while being considerably more, ahem, conservative in the description of left-wingers.
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We can see this even in the willingness to apply basic labels.
For example, Ta-Nehisi Coates "is an American author, journalist, and activist", who "wrote about cultural, social, and political issues, particularly regarding African Americans and white supremacy" but doesn't get called any kind of leftist or "progressive" for it. The page doesn't even use terms like "anti-racism". (They do at least have this all over the page for Ibram X. Kendi.) Noam Chomsky "is an American professor and public intellectual known for his work in linguistics, political activism, and social criticism." He "has been an influential voice on the American left as a consistent critic of U.S. foreign policy, contemporary capitalism, and corporate influence on political institutions and the media.", but this doesn't get him any labels in Wikipedia's own voice. Michael Moore "is an American film director, producer, screenwriter, and author" and you have to scroll down the page to see any reference to any terms describing any kind of leftism.
On the other hand, Kirk as of now "was an American right-wing political activist, entrepreneur, and media personality." and he has variously been called more fringe things during the edit warring. Ben Shapiro "is an American conservative political commentator, media host, and attorney." Candace Owens' "political positions have mostly been described as far-right or conservative.", in the second sentence (good on them for not treating it as an objective matter this time). Steven Crowder "is an American-Canadian conservative political commentator and Internet personality."
Wikipedia's page on Charlie Kirk claims, and has claimed for years, that
> Kirk promotes the Cultural Marxism conspiracy theory, and has described universities as "islands of totalitarianism."
at the top of a section currently titled "Promotion of falsehoods and conspiracy theories". Since May 6 2021 (https://en.wikipedia.org/w/index.php?title=Charlie_Kirk&diff...) there has been such a "Promotion of conspiracy theories" section, and even before that there was considerable edit warring over attempts to describe him as a "conspiracy theorist" in the first paragraph of the lede. (It doesn't appear to have this currently, but I have seen it like that since the assassination.)
The second part is a personal opinion, and unrelated to the first part. Two of the sources listed relate to the first part. One of these is from "Varsity Online", an "independent student newspaper for the University of Cambridge", which claims:
> Charlie Kirk, who was due to speak at the Union debate, has spoken out against what he sees as the proliferation of ‘cultural Marxism’ on campuses, and claimed in December that the gilet-jaunes protests in France were a “middle class rebellion against cultural Marxism”...
There is no attempt in this article to elaborate on what they think Kirk meant by this, nor to determine what he did mean by it. Which is presumably why they have the second source, which is an academic paper which attempts to define the term and brand it a conspiracy theory. The problem is, the paper doesn't mention Kirk. Using a term is not sufficient to establish that someone is pushing a related conspiracy theory; talking about, for example, the JFK assassination does not establish belief in any of the related conspiracy theories. Someone can easily hear a term like this and think it an accurate description, without having any idea about the conspiracy theory tied to it.
This sort of thing should be considered a blatant violation of WP:SYNTH and WP:BLP, and in my experience Wikipedia editors put immense effort into doing this sort of thing for prominent right-wingers while being considerably more, ahem, conservative in the description of left-wingers.
----
We can see this even in the willingness to apply basic labels.
For example, Ta-Nehisi Coates "is an American author, journalist, and activist", who "wrote about cultural, social, and political issues, particularly regarding African Americans and white supremacy" but doesn't get called any kind of leftist or "progressive" for it. The page doesn't even use terms like "anti-racism". (They do at least have this all over the page for Ibram X. Kendi.) Noam Chomsky "is an American professor and public intellectual known for his work in linguistics, political activism, and social criticism." He "has been an influential voice on the American left as a consistent critic of U.S. foreign policy, contemporary capitalism, and corporate influence on political institutions and the media.", but this doesn't get him any labels in Wikipedia's own voice. Michael Moore "is an American film director, producer, screenwriter, and author" and you have to scroll down the page to see any reference to any terms describing any kind of leftism.
On the other hand, Kirk as of now "was an American right-wing political activist, entrepreneur, and media personality." and he has variously been called more fringe things during the edit warring. Ben Shapiro "is an American conservative political commentator, media host, and attorney." Candace Owens' "political positions have mostly been described as far-right or conservative.", in the second sentence (good on them for not treating it as an objective matter this time). Steven Crowder "is an American-Canadian conservative political commentator and Internet personality."
For me at least, the search https://duckduckgo.com/?q=site%3Awikipedia.org+%22is+an+Amer... pulls up mostly people, while the search https://duckduckgo.com/?q=site%3Awikipedia.org+%22is+an+Amer... pulls up mostly websites and organizations. This is a clear form of bias (cf. https://slatestarcodex.com/2017/05/01/neutral-vs-conservativ...) that results from looking at media through the lens of the current interpretation of WP:RS.