If you talk to many Left Coasters (especially those in the PACNW especially Seattle), they are using the term more than ever intentionally being derogatory because of the Sonics situation. I've talked to/heard several people in Oregon/California say the same thing about "Okie's" regardless of the Sonics situation, but using it in a derogatory sense. When I was skiing at Angel Fire New Mexico last year, some people there were using it as a derogatory term and referring to our "dust bowl" type of state. Apparently, there are enough outsiders that still associate Okie with dust bowl, etc.
And I sure as heck don't want to be associated with these types of Okie's:
Okie Noodling
California had (and may still have) "The Anti-Okie Law".