Non-Marxist =/= Anti-Marxist. An anti-Marxist specifically believes Marx was wrong, a non-Marxist simply doesn’t follow the Marxist framework. Additionally, you can be a Marxist and think that more than half of Marx’s conclusions are wrong, what matters is the framework you’re using (historical materialism/scientific socialism). You can also agree with most of Marx’s conclusions and not be a Marxist, because you arrived at those conclusions by a different framework or just arbitrarily chose them (this is a simplistic characterization of incoherent ideology, but it’s good enough).

If you are curious about the prevalence of anti-Marxism, consider the fact that most people in a place like America have literally never heard the phrases “fictitious capital” or “reserve army of labor,” or perhaps they heard it in passing once but don’t remember hearing it.

Regarding Chomsky, it doesn’t answer your question directly, but there was an excellent series of essays called “Noam Chomsky and the Compatible Left” that used to be easily accessible online but appears to have been taken down. Perhaps an archival site has it. Here’s an archive of the first part: https://web.archive.org/web/20191115222100/https://lorenzoae.wordpress.com/2019/03/04/noam-chomsky-and-the-compatible-left-part-i/

It looks like it was only online for a brief period of time, so I guess I’m lucky that I happened to download it. I wish I had the same foresight with “In Search of a Soviet Holocaust” but, in fairness, that article was much older at the time and hosted on a reputable website.