Bert,
I take your point about the worldwide mutual contempt between town and country. I remember that in Aden, now in South Yemen, Budoui (Bedouin) was an insult and a popular song was "Denish keshiya" (I am not a farmer). But the word cowboy as a term of criticism has I think much more specific usage. It used I think to refer to the building trade but now has wider currency.