The author doesn't say that they are 'a pure diversion'. He wants to situate their life and work into what he calls the Global Theory Industry.

...For such a dialectical analysis, it is important to acknowledge that Adorno and Horkheimer did indeed mobilize their subjective agency in formulating significant critiques of capitalism, consumer society and the culture industry. Far from denying this, I would merely like to situate these criticisms within the objective social world, which entails asking a very simple and practical question that is rarely raised within academic circles: if capitalism is recognized as having negative effects, what is to be done about it? The deeper one mines down into their life and work, sifting through the deliberate obscurantism of their discourse, the more obvious their response becomes, and the easier it is to understand the primary social function of their shared intellectual project. For as critical as they sometimes are of capitalism, they regularly affirm that there is no alternative, and nothing can or should ultimately be done about it. What is more, as we shall see, their criticisms of capitalism pale in comparison to their uncompromising condemnation of socialism. Their brand of critical theory ultimately leads to an acceptance of the capitalist order since socialism is judged to be far worse. Not unlike most of the other fashionable discourses in the capitalist academy, they proffer a critical theory that we might call ABS Theory: Anything But Socialism.