Very good article with a lot of insight Ms Wente - or as Darth Vader would say; "most impressive."  I don't personally like to use the term "extremism"  although I know fully what you mean.  Many academics  on the left follow their patron Saint Herbert Marcuse's repressive tolerance doctrine.  Herbert Marcuse, hailed as “the Father of the New Left,”  was the author of “Repressive Tolerance” (1965).  He teaches that the establishment of a “liberating tolerance” will require the repression of certain people and all opposing points of view.   That is the situation we find in most liberal arts colleges  universities today. It is indoctrination of those who are open to indoctrination and repression of all those who are not,   The reason radical Black organizations like the Black Liberation Collective, Black Lives Matter, The Nation of Islam, and the New Black Panthers   get away with outrageous claims and behavior us due to both white guilt and the fear of being publicly labeled a racist.