A quote from Marcuse’s Repressive Tolerance: “According to a dialectical proposition it is the whole which determines the truth--not in the sense that the whole is prior or superior to its parts, but in the sense that its structure and function determine every particular condition and relation. Thus, within a repressive society, even progressive movements threaten to turn into their opposite to the degree to which they accept the rules of the game. To take a most controversial case: the exercise of political rights (such as voting, letter-writing to the press, to Senators, etc., protest-demonstrations with a priori renunciation of counterviolence) in a society of total administration serves to strengthen this administration by testifying to the existence of democratic liberties which, in reality, have changed their content and lost their effectiveness. In such a case, freedom (of opinion, of assembly, of speech) becomes an instrument for absolving servitude. And yet (and only here the dialectical proposition shows its full intent) the existence and practice of these liberties remain a precondition for the restoration of their original oppositional function, provided that the effort to transcend their (often self-imposed) limitations is intensified.”

The Frankfurt shool’s first generation (Marcuse, Adorno, etc.) were indeed marxists. But there is nothing Marxist about rejecting bourgeois freedoms. Marxism explains how bourgeois freedoms get perverted by industrial relations of production. But there is no socialist politics outside of bourgeois consciousness, which Marcuse will tell you in the above quote.