Question:
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.
Answer this question using a quote from the text above:

what did he have to do with social activism?

Answer:
Bernstein would go on to fight for everything from the influences of "American Music" to the disarming of western nuclear weapons.

Answer the question at the end by quoting:

Cosmo Kramer, usually referred to as simply "Kramer", is a fictional character on the American television sitcom Seinfeld (1989-1998), played by Michael Richards. The character is loosely based on comedian Kenny Kramer, Larry David's ex-neighbor across the hall. Kramer is the friend and neighbor of main character Jerry, residing in Apartment 5B, and is friends with George and Elaine. Of the series' four central characters, only Kramer has no visible means of support; what few jobs he holds seem to be nothing more than larks.
In "The Trip", Kramer admits that a man in a park exposed himself to him when he was a young boy. In "The Big Salad" Kramer reveals to Jerry that he grew up in a strict household where he had to be in bed every night by 9:00PM. In "The Letter", Kramer tells two art patrons that he ran away from home at age seventeen and stowed away aboard a steamer bound for Sweden. Kramer never completed high school; however, it is made clear in "The Barber" that Kramer has a GED. Kramer was estranged for a long period from his mom, Babs Kramer, who works as a restroom matron at an upscale restaurant. Unlike George and Jerry, Kramer's character does not have a well-developed network of family members shown in the sitcom. He is the only main character on the show whose dad never makes an appearance; however, in "The Chinese Woman", Kramer mentions that he is the last male member of his family, implying that his father had died. He also mentions in "The Lip Reader" that he has or had a deaf cousin, from whom he learned fluent American Sign Language, but when Kramer tries to communicate in ASL, he speaks complete gibberish and cannot correctly translate the ASL he sees others using. He also apparently has no biological children, although he adopted mile 114 of the Arthur Burkhardt Expressway in "The Pothole". During an opening discussion, Kramer reveals to Jerry that in 1979 he was struck on the head by a falling air conditioner while walking on the sidewalk. Jerry asks if that was when Kramer lived in Greenwich Village, to which Kramer replies that he cannot remember. This is discussed in the beginning of "The Little Kicks". In "The Strong Box", it is revealed that Kramer spent a brief time in the Army, although info about this time is "classified". In episode three of season one he says he lived in Los Angeles for three months.

How was his home life, parents, siblings etc?
Kramer reveals to Jerry that he grew up in a strict household where he had to be in bed every night by 9:00PM.