What I know of Karp that suggests that he's left is that studied under Habermas of the Frankfurt School, whose social theses is about as academically left wing

What I know of Karp that suggests that he's left is that studied under Habermas of the Frankfurt School, whose social theses is about as academically left wing as you can get. The Frankfurt School's critiques had once been very popular in the US where it was imported as critical theory. Horkheimer and Ardono of the Frankfurt School criticized the consumerization of culture that is present everywhere in US society: recall that before mass communications popular culture was pretty much local, handmade, diverse and free, but these days it is mediated by big companies that produce flashy, generic products: think Disney, Hollywood and Hallmark; already in the 1930s this US tendency to commercialize was present to those continential Europeans. They saw that this commercial culture was soft propaganda for a capitalist society, distracting people from the reality of their situation; in this manner, unjust societies like capitalism can maintain their division of power. Unfortunately I'm even less familiar with Habermas's work. In any case, it seems to me that the Anglosphere is not very receptive of the Frankfurt School. Most of their works seem to suffer from an overemphasis in engaging in a dialectic with previous philosophers and reinterpreting old theories, rather than actually doing fieldwork and find if there is evidence that those theories (and their own) are good explanations or summaries of reality. (Less kind people would say that all this is a charade at seeming intellectual without doing any good science or philosophy)