McCarthyism

[muh-kahr-thee-iz-uh m] /məˈkɑr θiˌɪz əm/

noun
1.
the practice of making accusations of disloyalty, especially of pro-Communist activity, in many instances unsupported by proof or based on slight, doubtful, or irrelevant evidence.
2.
the practice of making unfair allegations or using unfair investigative techniques, especially in order to restrict dissent or political criticism.
/məˈkɑːθɪˌɪzəm/
noun (mainly US)
1.
the practice of making unsubstantiated accusations of disloyalty or Communist leanings
2.
the use of unsupported accusations for any purpose

1950, with -ism + name of U.S. Sen. Joseph R. McCarthy (1908-1957), leader of U.S. anti-Communist agitation. The term is said to have been coined by “Washington Post” political cartoonist Herbert Block (“Herblock”). The surname is from Irish Mac Carthaigh “son of Carthach” (Welsh Caradawc), an ancient Celtic name, also known in its Latinized form, Caractacus (last of the British leaders to resist Rome, captured 51 C.E.)

The extreme opposition to communism shown by Senator Joseph R. McCarthy and his supporters in the 1940s and 1950s.

Note: McCarthyism has become a general term for the hysterical investigation of a government’s opponents or the publicizing of accusations against these opponents without sufficient evidence to support the charges.