"Martin David Kahane;[1] August 1, 1932 – November 5, 1990) was an American-born Israeli Orthodox ordained rabbi"

"Infiltrating the John Birch Society
In the late 1950s and the early 1960s, Kahane's life of secrecy and his strong anticommunism landed him a position as a consultant with the FBI. According to his wife, Libby, his assignment was to infiltrate the anticommunist John Birch Society and report his findings to the FBI.[19]"

https://en.wikipedia.org/wiki/Meir_Kahane

Snitched on them to support them