Jewish Radicalism and the Red Scare

If you want to understand the intersection between anti-semitic attacks on Bernie Sanders from both the right and the right-side of the Democratic Party, you should understand some of the relevant history.

Here is a good starting point for those who may not be aware of it.
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http://jwa.org/teach/livingthelegacy/jewish-radicalism-and-red-scare-introductory-essay

There is a strong tradition of Jewish radicalism, which began in earnest in the late 19th century. Some Jews became radicals in Eastern Europe, but many first encountered radical politics such as Socialism or Communism as immigrant workers in American cities. The Jewish radical community swelled after 1905 as Jewish immigrants fled persecution from the revolutions sweeping across Russia. In America, radical politics and the labor movement became new forms of Jewish expression—“purely secular” and “thoroughly Jewish” as activist Yankel Levin described it in 1918. Jewish socialists saw themselves as creating a new model of the Jew: worldly, activist, and broad-minded. Yiddish culture, expressed both in political activities and in cultural forms (literature, theater, etc.), was at the center of this new Jewish world. From this cultural flourishing emerged a new image of the Jew as radical—an influential characterization during the Progressive Era.

Yet even in such an open political environment as the democratic society of the U.S., radicals have been persecuted in certain periods. This often occurred during or after wars or other periods of vulnerability; the 1920s, after the end of World War I, for example, saw the first “Red Scare,” an attack on Socialists, Communists, and labor organizers (named after the color of the flag of the newly created Soviet Union). Another Red Scare occurred after World War II, a period also referred to as the “McCarthy Era” after Senator Joe McCarthy who made his name pursuing and persecuting “Communist sympathizers.” From 1946 through the early 1960s, American citizens suspected of being sympathetic to the Soviet Union or Communism, or who were thought to have radical political views in general, were investigated, arrested, imprisoned, fined, fired from their jobs, and barred from future employment in their fields. People lost their careers, their friends, and sometimes even their families. Ordinary people were encouraged to spy on their neighbors and friends and to report any suspicions of “subversive” activity (any activity that could in some way be seen as undermining American political democratic and capitalist culture). This might mean saying something that sounded sympathetic to Communism or leftist politics, going to Communist Party (CP) meetings (it was not actually illegal to be a member of the CP), socializing with friends who were being investigated for Communist activity, etc.

Some of those involved in the House Un-American Activities Committee (the Congressional committee charged with investigating subversive behavior) were overtly anti-Semitic. For example, Representative John Rankin was a member of the Ku Klux Klan and known for his blatant anti-Semitism toward fellow Congressmen. Many Jews suspected that HUAC chose to focus on Hollywood because of its large Jewish presence and the prominent role of Jews in building the studio system. Six of the “Hollywood Ten”—the ten original “unfriendly witnesses” (those who would not cooperate with HUAC’s demand that they identify Communists) indicted and imprisoned by HUAC in 1947—were Jewish. They were all blacklisted until the 1960s or 1970s.