Non-Sectarian Anti-Nazi League
The Non-Sectarian Anti-Nazi League to Champion Human Rights (originally the American League for the Defense of Jewish Rights) was founded in 1933 by the Jewish Samuel Untermyer to lobby for many boycotts against National Socialist Germany.
Throughout the 1930s, allied with groups such as the American Federation of Labor, the league tried to persuade American businesses to stop purchasing merchandise from Germany, exposing the ones that continued selling German-made goods. It also lobbied the United States government, asking it to investigate various things, such as claimed National Socialist propaganda. The organization propagandized to the general public through radio and by distributing printed material. It also provided "information" to the House Un-American Activities Committee.
In the postwar period, it changed its mission to directly investigate right-wing propaganda groups. It also begun to support the Civil Rights Movement. The organization filed a lawsuit against Columbia University to have its tax except status revoked for claimed discrimination against Jews. See Jewish quota.
Leftist Wikipedia claims that "The League was able to successfully combat the resurgence of hate groups in the U.S. by infiltrating the Ku Klux Klan", presumably referring to a single Klan organization, the "Georgia Ku Klux Klan". Wikipedia also clams that the investigator Stetson Kennedy was "exposing their secrets on the popular children's radio program The Adventures of Superman, trivializing their rituals." Supposedly, Kennedy's actions led to the state of Georgia to revoke the Klan's corporate charter. Wikipedia is somewhat unsure regarding the reliability of Stetson Kennedy's claims.
The League dissolved in 1975 with the death of its last head and had been inactive for some time before this.