“In the warmest of hearts, there’s a cold spot for the Jews” means that even among the kindest people, there’s always seems to be some anti-Semitism. The screenwriter Ben Hecht (1894-1964) wrote:
 
“How sad that in the warmest hearts I knew lurked always a little cold spot for the Jew.”
 
New York literary critic Irving Howe (1920-1993) wrote in 1971 in the New York (NY) Times that “as someone has remarked, in the warmest of hearts there’s a cold spot for the Jews.” In a 1973 New York magazine article, Howe called this a “sour apothegm.” Irving Howe has often received credit for Hecht’s saying.
 
       
Wikipedia: Ben Hecht
Ben Hecht (/ˈhɛkt/ hekt; 1894–1964) was an American screenwriter, director, producer, playwright, and novelist. Called “the Shakespeare of Hollywood”, he received screen credits, alone or in collaboration, for the stories or screenplays of some 70 films and as a prolific storyteller, authored 35 books and created some of the most entertaining screenplays and plays in America. Film historian Richard Corliss called him “the” Hollywood screenwriter, someone who “personified Hollywood itself.” The Dictionary of Literary Biography - American Screenwriters calls him “one of the most successful screenwriters in the history of motion pictures.”
 
He was the first screenwriter to receive an Academy Award for Original Screenplay, for the movie Underworld (1927). The number of screenplays he wrote or worked on that are now considered classics is, according to Chicago’s Newberry Library, “astounding,” and included films such as, Scarface (1932), The Front Page, Twentieth Century (1934), Barbary Coast (1935), Nothing Sacred (1937), Some Like It Hot, Gone with the Wind, Gunga Din, Wuthering Heights, (all 1939), His Girl Friday (1940), Spellbound (1945), Notorious (1946), Monkey Business, A Farewell to Arms (1957), Mutiny on the Bounty (1962), and Casino Royale (released posthumously, in 1967). He also provided story ideas for such films as Stagecoach (1939). In 1940, he wrote, produced, and directed, Angels Over Broadway, which was nominated for Best Screenplay. In total, six of his movie screenplays were nominated for Academy Awards, with two winning.
 
He became an active Zionist shortly before the Holocaust began in Germany, and as a result wrote articles and plays about the plight of Europe’s Jews, such as We Will Never Die in 1943 and A Flag is Born in 1946. Of his seventy to ninety screenplays, he wrote many anonymously to avoid the British boycott of his work in the late 1940s and early 1950s. The boycott was a response to Hecht’s active support of paramilitary action against British forces in Palestine, during which time a supply ship to Palestine was named the S.S. Ben Hecht.
 
Wikipedia: Irving Howe
Irving Howe (June 11, 1920 – May 5, 1993) was an American literary and social critic and a prominent figure of the Democratic Socialists of America.
   
Google Books
A Treasury of Ben Hecht;
Collected stories and other writings
By Ben Hecht
New York, NY: Crown Publishers
1959
Pg. 46:
POET (reciting pensively).
How sad that in the warmest hearts I knew
Lurked always a little cold spot for the Jew.
 
13 March 1971, New York (NY) Times, “The Campus Left and Israel” by Irving Howe, pg. 29:
...as someone has remarked, in the warmest of hearts there’s a cold spot for the Jews.
 
Google Books
Israel, the Arabs, and the Middle East
By Irving Howe and Carl Gershman
New York, NY: Quadrangle Books
1972
Pg. 428:
Part of that turn may be the result of a century-old sentiment always at work in our civilization: as someone has remarked, in the warmest of hearts there’s a cold spot for the Jews.
 
Google Books
24 December 1973, New York magazine, “Thinking the Unthinkable About Israel: A Personal Statement” by Irving Howe, pg. 45, col. 3:
Our common support of Israel rests on the fact that both of us, if in different ways, believe in democracy;  both of us are Jews; and both of us have lived long enough to recognize a portion of truth in the sour apothegm: In the warmest of hearts there’s a cold spot for the Jews.
(Speaking about Irving Kristol—ed.)
 
Google Books
Why the Jews?:
The reason for antisemitism
By Dennis Prager and Joseph Telushkin
New York, NY: Simon & Schuster
1983
Pg. 150:
It was regarding this Leftist hatred of the Jews that Social Democrat Irving Howe wrote, “In the warmest of hearts there is a cold spot for the Jews.”
 
24 June 1990, Jerusalem Post, “Salutes that are never returned” by Sidney Zion, pg. 4:
The terrible sadness is, as Ben Hecht also said: “In the warmest of hearts there is a cold spot for the Jews.”
 
Google Books
The Fateful Triangle:
The United States, Israel and the Palestinians
By Noam Chomsky
Cambridge, MA: South End Press
1999
Pg. 15:
Similarly Irving Howe, typically without argument, simply attributes Israel’s dangerous international isolation to “skillful manipulation of oil” and that “sour apothegm: In the warmest of hearts there’s a cold spot for the Jews” — so that it is quite unnecessary to consider the impact of the policies of the Labor government that he supported, for (Pg. 16—ed.) example, the brutality of the occupation, already fully apparent and sharply condemned in Israel when he wrote.
 
An American Journey
Posted on June 28, 2005
Atlanta, Day 2
From Justin Levy:
Saul Bellows said “In the warmest of hearts, there is a cold spot for the Jews”.
   
Solomonia
Monday, July 23, 2007
Dershowitz: Carter’s selective sensitivity
(...)
COMMENTS
#3 Joanne | July 23, 2007 1:35 PM
This reminds me of a quote from that fine Jewish-American intellectual, the late Irving Howe. He said that “even in the warmest of hearts, there’s a cold spot for the Jews.”
 
International Business Times
Israel Grows More Isolated
By Walt Osterman: Subscribe to Walt’s RSS feed
February 23, 2012 2:50 PM EST
There is an old adage: Even in the warmest of hearts, there’s a cold spot for the Jews.
 
Just yesterday, Russia warned Israel not to strike Iran. Iran’s government, feeling its oats, responded by threatening to attack Israel preemptively. And President Barack Obama has turned his gaze elsewhere. Americans have historically been Israel’s No. 1 ally, but that no longer appears to be the situation.