Under a system of constitutionally guaranteed and (generally and without too many and too glaring exceptions) practiced civil rights and liberties, opposition and dissent are tolerated unless they issue in violence and/or in exhortation to and organization of violent subversion. The underlying assumption is that the established society is free, and that any improvement, even a change in the social structure and social values, would come about in the normal course of events, prepared, defined, and tested in free and equal discussion, on the open marketplace of ideas and goods.[2] Now in recalling John Stuart Mill’s passage, I drew attention to the premise hidden in this assumption: free and equal discussion can fulfill the function attributed to it only if it is rational expression and development of independent thinking, free from indoctrination,manipulation, extraneous authority.
https://www.marcuse.org/herbert/publications/1960s/1965-repressive-tolerance-fulltext.html