"Untermeyer ... continued to be active in campaigning for left-wing causes and as a result the FBI had been collecting a file of his activities. His name was also mentioned during the House of Un-American Activities Committee investigation into communist subversion. This was brought to the attention of the television industry and in 1951 Untermeyer was sacked from the television show and was blacklisted. Like many left-wing artists during this period, Untermeyer became a victim of McCarthyism.
"In his autobiography, Timebends - A Life (1987), Arthur Miller, explained how Untermeyer responded to this victimization: 'Louis went back to his apartment. Normally we ran into each other in the street once or twice a week or kept in touch every month or so, but I no longer saw him in the neighborhood or heard from him. Louis didn't leave his apartment for almost a year and a half. An overwhelming and paralyzing fear had risen him. More than a political fear, it was really that he had witnessed the tenuousness of human connection and it had left him in terror. He had always loved a lot and been loved, especially on the TV program where his quips were vastly appreciated, and suddenly, he had been thrown into the street, abolished.'"
Married four times, to Jean, Virginia, Esther, then Bryna.