Added footnote:
'Honky' as a perjorative is earlier than 1967- Mezzrow, in Mezzrow and White, 1946, "Really Blues"; possibly- since he may have been referring to 'Hunkies;' "Man, I'm down with it, stickin' like a honky."
In 1958, the film "Defiant Ones," "[You're a] nigger...I'm a honky. You don't have to argue me out of it."
1967- "Time," Aug. 4.: Damning Lyndon Johnson for sending "honky" cracker federal troops into Negro communities to kill Black people, Brown called the president "a wild, mad dog, an outlaw from Texas..."

No relation to the old western American word honkatonk or honkytonk (1894 or earlier).

Above quotes from Lighter, "Historical Dictionary of American Slang," vol. 1.