Answer by taking a quote from the following article:

Leonard Bernstein ( BURN-styne; August 25, 1918 - October 14, 1990) was an American composer, conductor, author, music lecturer, and pianist. He was among the first conductors born and educated in the US to receive worldwide acclaim. According to music critic Donal Henahan, he was "one of the most prodigiously talented and successful musicians in American history."

While Bernstein was very well known for his music compositions and conducting, he was also known for his outspoken political views and his strong desire to further social change. His first aspirations for social change were made apparent in his producing (as a student) a recently banned opera, The Cradle Will Rock, by Marc Blitzstein, about the disparity between the working and upper class. His first opera, Trouble in Tahiti, was dedicated to Blitzstein and has a strong social theme, criticizing American civilization and suburban upper-class life in particular. As he went on in his career Bernstein would go on to fight for everything from the influences of "American Music" to the disarming of western nuclear weapons.  Like many of his friends and colleagues, Bernstein had been involved in various left wing causes and organizations since the 1940s. He was blacklisted by the US State Department and CBS in the early 1950s, but unlike others his career was not greatly affected, and he was never required to testify before the House Un-American Activities Committee. His political life received substantial press coverage though in 1970, due to a gathering hosted at his Manhattan apartment on January 14, 1970. Bernstein and his wife held the event seeking to raise awareness and money for the defense of several members of the Black Panther Party against a variety of charges. The New York Times initially covered the gathering as a lifestyle item, but later posted an editorial harshly unfavorable to Bernstein following generally negative reaction to the widely publicized story. This reaction culminated in June 1970 with the appearance of "Radical Chic: That Party at Lenny's", an essay by satirist Tom Wolfe featured on the cover of the magazine New York. The article contrasted the Bernsteins' comfortable lifestyle in one of the world's most expensive neighborhoods with the anti-establishment politics of the Black Panthers. It led to the popularization of "radical chic" as a critical term. Both Bernstein and his wife Felicia responded to the criticism, arguing that they were motivated not by a shallow desire to express fashionable sympathy but by their concern for civil liberties.  Bernstein was named in the book Red Channels: The Report of Communist Influence in Radio and Television (1950) as a Communist along with Aaron Copland, Lena Horne, Pete Seeger, Artie Shaw and other prominent figures of the performing arts. Red Channels was issued by the right-wing journal Counterattack and was edited by Vincent Hartnett, who was later found to have libeled and defamed the noted radio personality John Henry Faulk.

Was he critized?
He was blacklisted by the US State Department and CBS in the early 1950s,