Tom Smothers performed on The Smothers Brothers Comedy Hour, an American comedy and variety show television series from 1979 to 1969. The network didn’t like some of the political satire and cancelled the show.
 
“‘The only valid censorship of ideas,’ he (Tom Smothers—ed.) said, ‘is the right of people not to listen’” was printed in the San Francisco (CA) Examiner on August 23, 1969. “The only valid censorship of ideas is the right of people not to listen” has been printed on many images.
 
     
Wikipedia: Tom Smothers
Thomas Bolyn Smothers III (born February 2, 1937) is an American comedian, composer and musician, best known as half of the musical comedy duo the Smothers Brothers, alongside his younger brother Dick.
     
Wikipedia: The Smothers Brothers Comedy Hour
The Smothers Brothers Comedy Hour was an American comedy and variety show television series hosted by the Smothers Brothers and initially airing on CBS from 1967 to 1969.
 
The series was a major success, especially considering it was scheduled against the major NBC television series Bonanza, with content that appealed to contemporary youth viewership with daring political satire humor and major music acts such as Buffalo Springfield, Pete Seeger, Cream, and The Who. Despite this success, continual conflicts with network executives over content led to the show being abruptly pulled from the schedule in violation of the Smothers’ contract in 1969.
 
Newspapers.com
23 August 1969, San Francisco (CA) Examiner, “Tommy Smothers Plays Local Club” by James Schermerhorn, pg. 3, col. 6:
“The only valid censorship of ideas,” he (Tom Smothers—ed.) said, “is the right of people not to listen.”
       
Google Books
Quote Unquote (A Handbook of Quotations)
By M.P. Singh
New Delhi, India: Lotus Press
2006
Pg. 70:
“The only valid censorship of ideas is the right of people not to listen.” — Tommy Smothers
 
Google Books
Quote/Unquote:
Quotations on freedom of speech, journalism, the news media and the world of words
Edited by Lizette Rabe
South Africa: Rapid Access Publishers
2016
Pg. 31:
The only valid censorship of ideas is the right of people not to listen.
Tommy Smothers (1937-)
American comedian
 
Reddit—Quotes
Posted by u/Colinmacus May 23, 2017
“The only valid censorship of ideas is the right of people not to listen.” ― Tommy Smothers
 
Twitter
Ⓥ NAP Paul Ⓐ
@PaulTheMartian
“The only valid censorship of ideas is the right of people not to listen.”
Tom Smothers
10:21 AM · Mar 12, 2019·Twitter for iPhone