Because that is the most prominent application of postmodernism: to push forward neo-Marxist ideology.
Because that is the most prominent application of postmodernism: to push forward neo-Marxist ideology.
'Cultural Marxism' is a pejorative term for the Frankfurt School of Critical Theory. It was invented by fascists to dismiss the whole enterprise without engaging with it.
The Frankfurt School emerged in the 1920s/30s in response to the failure of the proletariat to overthrow capitalism in the way that Marx had suggested would happen, and as a response to the crude economism of a lot of early Marxism (i.e. where 'culture' was just an epiphenomenon rooted in the economic base of a society). It was a German school - its main sources were Hegel, Marx, Mannheim, etc.
Post-modernism, on the other hand, is a term for a very amorphous group of (largely French) thinkers who reacted against the dominance of structuralist social theory in the 1960s, which itself was a reaction to existentialism. Its sources are usually the canon of phenomenology, the structuralists before them, and Nietzsche.
The Frankfurt School is best known for its formulation of ideological critique, its critique of 'instrumental rationality', its holistic view of a critical social science, and its collected writings on aesthetics and mass media.
The post-modernists are best known for their rejection of a lot of the heritage of the Enlightenment, their focus on the fragility and contingency language, and their emphasis on 'play, metaphor, rhizomes', etc. But they are not a single school - they are FAR more varied than the Frankfurt School. For example, Pierre Bourdieu (who had a fairly empirical sociology of cultural hierarchy and class) is worlds away from Jacques Derrida (who was an abstract theorist that wrote very opaquely, and IMO is responsible for a lot of the bad reputation of post-modernism).
There's simply no evidence for it; Peterson's confusion is his own and I hope that others do not follow him on this and instead choose to do their own research into philosophy.
His evidence is presumably his own conversations with postmodernists, and his theory as to why this is seems based more in a psychological than philosophical framework.