Historical change in the use of "dude" in 60's US

J.E. Lighter, Random House Historical Dictionary of American Slang ((1994) indicates that dude in the sense of "a male person; fellow" has been around since the late 1800s, although the usage picked up considerably in the late 1960s:

dude n. {orig. unkn.} ... 2.a. a male person; fellow. {Esp. common since the late 1960's; Staub 1918 quot. extends the sense to horses and mules.} [Examples:] 1883 Peck Bad Boy 284: I get to thinking about Adam and Eve in the garden of Eden, and of the Dude with the cloven hoof that flirted with Eve. Ibid. 333: Eve...got mashed on the the old original dude, and it stnds to raeson that Solomon's wives were no better. 1895 Townsend Fadden 21: Say, I was kinder layin' fer dat dude, anyhow, cause 'e is allus roastin' me. 1912 Chi[cago] Defender (Oct. 26) 3: The dudes...worked on the S.S. Minnesota this summer. 1916 Chi[cago] Defender (July 15) 6: Guess Who...the doll...is who is fast becoming popular with all the dudes. Ibid. You sure made more than one dude look twice at you, girlies. 1918 Ruggles Navy Explained 139: In a gang of snipes below there is generally one dude who is known as the "king snipe." He is considered the leading snipe of the watch. 1918 Straub Diary {entry for June 23} Armstrong and I helped some of the Battalion men load some of their horses and mules because it is certainly a job to get the old "dudes" into a car without fighting with some of them. 1918–19 MacArthur Bug's-Eye View 93: Listen to this guy!...Here they're pegging shells at us like confetti, and this dude is trying to sell me a helmet. 1919 Johnson Heaven, Hell, or Hoboken 21: Things We Hated..."Gimme a cigarette" (twenty times a day from the same dude.) Ibid. 119: The new men from the 86th Division came to us at the Gully. Remember how we felt for the poor dudes? 1921 Pirate Piece (Apr.) 3: Now you here dudes have got to give m a lift on this thing. 1923 McKnight Eng[lish] Words 62: The girls' list of names for member of the other sex is nearly as rich. Noncommittal in general are: dude, goof, john,...guy, kid. 1933–35 D. Lamson About to Die 37: I been watching them dudes {convict workmen} up there for the last fifteen minutes. Ibid. 200: And suppose some other dude starts another shop across the street. 1940 Lawes Murderer 271 {ref. to 1933}: Maybe they'll give 'em a chance to grab some other dude before he's in a spot like me. 1963 Braly Shake Him 53: Just you dudes in this? 1965 Wade & Kassebaum Women's Pros[on] 122: They can't wait to get with a dude {man} again. 1967 Taggart Reunion 63: Now who the hell was that dude? 1967 Yablonsky Hippie Trip 76: This cat, a beautiful dude, gave drugs to anybody who wanted it. 1968 Carey College Drug Scene 16: And I got into symbolic logic and semantics with a cat who had studied with Korzybski and electronics from a dude who had an Associate of Arts degree from 1941. 1968 N.Y. Post (Aug. 14) 5: I shot two dudes (policemen). 1970 A. Young Snakes 91: Dudes, chicks, little children. 1970 M. Thomas Beast 245: What kind of dude was he? 1974 Strasburger Rounding Third 2: So let's us shrewd dudes not go fooling anyone, all right?

It is noteworthy that the Chicago Defender (which Lighter cites as the source of the 1912 and 1916 instances) was an African American–focused newspaper. However, George Wilbur Peck, author of Bad Boy (cited in Lighter's 1883 instances) was a white newspaperman and politician from Wisconsin; and Edward W. Townsend, author of the "Chimmie Fadden" Bowery boy stories cited in Lighter's 1895 instance) was a white newspaperman and politician who lived in Cleveland, Ohio; Sn Francisco, California, New York City; and Montclair, New Jersey.

An untitled item in The Nation (October 25, 1883) mentions a lecturer who takes the then-more-narrowly-understood term dude and applies it in a pejorative sense to "all sorts of persons with whom he does not agree or does not approve of":

The application of the term "dude" to a particular kind of dandy has led to the use of it by a great many people as a term of reproach for all well-dressed persons whom they dislike, and like all nicknames, is a labor-saving invention. Mr. Tourgée, the author of 'The Fool's Errand,' who has taken to lecturing, without any very good reason as far as we can see, has now turned the term to better account than ever by preparing a lecture on the dude. He uses the word to describe all sorts of persons with whom he does not agree or does not approve of. He has his literary dudes, and his political dudes, and his fashionable, sporting, and artistic dudes; but from his account of them one can see no reason in the world for calling them dudes, except that Mr. Tourgée does not like them. He might just as well call them kangaroos or prairie-dogs.

Here we see an early instance of generalizing the term dude so that it applies to a person without conveying any particular attribute—or anything at all, except the speaker's hostility. And when the hostility drops out, the only thing left is a generic term for a male person. Something similar seems to have happened with the words fellow and guy in earlier eras.

Lighter's examples notwithstanding, neither Harold Wentworth & Stuart Flexner, Dictionary of American Slang (1960) nor Wentworth & Flexner Dictionary of American Slang, supplemented edition (1967) includes a definition of dude in its generalized sense of "male person." The first version of this series to include such a definition is Wentworth & Flexner, Dictionary of American Slang, second supplemented edition (1975), which offers this:

dude n. A man; fellow; guy; any male person. 1973: "I'm siittin' in the bus stop ... just me and these three other dudes. ..." D. Evans, Black World, Apr., 65. Negro use.

This last edition of Wentworth & Flexner seems unaware of the line of similar usage from the late 1800s through World War I and on through the 1920s and 1930s that Lighter documents.

Also of possible interest is this entry for dude in Clarence Major, Juba to Jive: A Dictionary of African-American Slang (1994):

Dude n. (1960s–1980s) black male term of address; any sharp , smart, respected man or boy. Derived from "duds"; a "dudsman" dealt in clothes [with citations to Terry McMillan, Disappearing Acts (1989); Eric Partridge, A Dictionary of the Underworld, British and American (1949/1961); Christina Milner & Richard Milner, Black Players (1971); and Pamela Munro, UCLA Slang (1989)]

However, Clarence Major, Dictionary of Afro-American Slang (1970) has no entry for dude.

Hyman Goldin, Frank O'Leary & Morris Lipsius, Dictionary of American Underworld Lingo (1950), on the other hand, offers this extremely pertinent entry:

Dude. A person; a fellow.

It thus appear that dude in the sense of "a male person" was current in "underworld English" by 1950 after having appeared sporadically in the same sense for many decades prior to that. Current usage of the term seems to have been heavily influenced by popularized African American usage during the 1960s and later, but the term may have been floating around in—and perhaps crossing back and forth between—various subcultures in the United States from at least 1885 onward.

The following extract supports the African-American thesis citing the OED:

In the 20th century, “dude” evolved to take on a more neutral meaning. The term was adopted in the black community, then as now a prime spreader of new words and meanings.

This 1967 OED example reflected the shift in meaning: “My set of Negro street types contained a revolving and sometimes disappearing (when the ‘heat’, or police pressure, was on) population... These were the local ‘dudes’, their term meaning not the fancy city slickers but simply ‘the boys’, ‘fellas’, the ‘cool people’.”

In the sixties the term attracted more coolness as it was embraced by surf culture, and by the seventies, a dude was just a guy.

(www.good.is)