In recent years I've seen far right, conservative, and right libertarian groups (most recently Ron Paul) propagate images and writings about something they call "cultural Marxism", which if I understand it correctly is some sort of theory in Marxism that western culture must be undermined or destroyed, often in relation to immigration. Also it seems to frequently be accompanied with references to later Marxists, usually of the Frankfurt School like Adorno, Marcuse et al.

However leftists I know often dismiss this as a conspiracy theory.

Did Marx write about culture much? What did he say? Was he critical of western culture?

Regarding the Frankfurt school I had been under the impression that Adorno believed culture was undermined or damaged by capitalism, is this correct? How then has he and his compatriots become associated with wanting to destroy it?

Thanks in advance for any information you can provide.