“A writer must always tell the truth (unless he’s a journalist)”

American writer Gore Vidal (1925-2012) wrote in The American Presidency (1998):
   
“But I was born a writer, and a writer must always tell the truth (unless he’s a journalist), ...”
   
“A writer must always tell the truth (unless he’s a journalist)” is the clipped form of the quotation, as it has been printed on several images.
   
     
Wikipedia: Gore Vidal
Eugene Louis “Gore” Vidal (/ˌɡɔːr vᵻˈdɑːl/ October 3, 1925 – July 31, 2012) was an American writer and public intellectual known for his patrician manner, epigrammatic wit, and polished style of writing.
   
Google Books
The American Presidency
By Gore Vidal
Monroe, ME: Odonian Press
1998
Pg. 27:
But I was born a writer, and a writer must always tell the truth (unless he’s a journalist), ...
 
Twitter
Gary Grossman‏
@GaryGrossman1
“A writer must always tell the truth (unless he’s a journalist).” 
-Gore Vidal, The American Presidency
follow me @garygrossman1
10:09 AM - 15 Apr 2012
 
BBC News
Gore Vidal: In quotes
1 August 2012
Celebrated author, satirist and political commentator Gore Vidal has died, aged 86. He was famed for his biting political critiques and his acerbic take on American society. Here are some of his best quotes.
(...)
On the press
“A writer must always tell the truth, unless he is a journalist.”
 
5 August 2012, The People (London, UK), pg. 25:
?MY favourite quote by America’s waspish self-styled “gentleman bitch” Gore Vidal, who closed the book last week aged 86: “Every time a friend succeeds, I die a little.” My second favourite quote: “A writer must always tell the truth, unless he’s a journalist.”
—Charlie Catchpole