Newspaper columnist and author Walter Lippmann (1889-1974) wrote in Liberty and the News (1920):
 
“There can be no higher law in journalism than to tell the truth and shame the devil.”
 
The phrase “to tell the truth and shame the devil” was used by William Shakespeare and others in the 16th century, and it means that one should tell the truth, despite many temptations not to do so. Lippmann’s statement is frequently quoted in works about journalism.
 
   
Wikipedia: Walter Lippmann
Walter Lippmann (September 23, 1889 – December 14, 1974) was an American public intellectual, writer, reporter, and political commentator famous for being among the first to introduce the concept of Cold War; he coined the term stereotype in the modern psychological meaning as well. Lippmann was twice awarded (1958 and 1962) a Pulitzer Prize for his syndicated newspaper column, “Today and Tomorrow”.
 
The Phrase Finder
While you live, tell truth and shame the Devil!
Meaning
Tell the truth, even when tempted to lie.
Origin
The preacher Hugh Latimer recorded this as a ‘common saying’ as early as 1555, in his Twenty Seven Sermons:
 
“There is a common saying amongst vs, Say the truthe and shame the diuel.”
   
Google Books
Liberty and the News
By Walter Lippmann
New York, NY: Harcourt, Brace and Howe
1920
Pg. 13:
There can be no higher law in journalism than to tell the truth and shame the devil.
 
Google Books
Never Tire of Protesting
By George Seldes
New York, NY: L. Stuart
1968
Pg. 275:
Shakespeare’s Henry IV said, “While you live, tell truth and shame the devil,” and only recently our leading columnist, Walter Lippmann, wrote that “there is no higher law in journalism than to tell the truth and shame the devil.” You might even shame the pres Lords.
 
Google Books
Broadcast Journalism
By Andrew Boyd
Woburn, MA: Focal Press
2001
Pg. 196:
There can be no higher law in journalism than to tell the truth and shame the devil . . . Remain detached from the great.’ – WALTER LIPMANN, US JOURNALIST
 
Google Books
Watching the Sun Rise:
Australian Reporting of Japan, 1931 to the Fall of Singapore
By Jacqui Murray
Lanham, MD: Lexington Books
2004
Pg. 127:
There could be “no higher law in journalism than to tell the truth and shame the devil.” Without truth, Lippman warned, incompetence, “aimlessness, corruption and disloyalty, panic and ultimate disaster, must come to any people which is denied an assured access to the facts.” Few such voices were heard in Australia.
   
CBS News
By MATTHEW FELLING / CNET/ July 3, 2007, 4:13 PM
Best. Journalism Quotes. Ever.
(...)
Number 8:
There can be no higher law in journalism than to tell the truth and to shame the devil.
Walter Lippmann