If the OP was using it in this way, I don't see the issue. If he/she was using it to just describe laboring, rural whites, I agree; it's offensive and inappropriate. Given the context of the statement, I assumed the former.
https://en.wikipedia.org/wiki/Redneck
On the topic, Randy Newman's song "Rednecks" is a scathing critique of Northerners and their "hidden" racism and hypocrisy on the subject.
>Yes he's free to be put in a cage In Harlem in New York City And he's free to be put in a cage On the South Side of Chicago And the West Side And he's free to be put in a cage In Hough in Cleveland And he's free to be put in a cage In East St. Louis And he's free to be put in a cage In Fillmore in San Francisco And he's free to be put in a cage In Roxbury in Boston They're gatherin' 'em up from miles around . . . (apologies for the formatting)