Some of my best friends are Jews

[GEORGE THOMPSON]

On behalf of a friend on the faculty here:

When did the expression "some of my best friend are jews" come to be
offered as the standard marker of a speaker who was at least
marginally prejudiced.  (Or, the parallel "Some of my best friends
are colored.")  Robert Gessner, a mentor of hers 60+ years ago,
published a book with this title in 1936.  Given that its subject is
anti-semitism in Europe of the time, I suppose that the title was
taken ironically, that the expression was already recognized as
usually leading to a "but . . . ."  She'd like confirmation.

GAT