The word 'redneck'is highly offensive and is used by mainly American communists and milder pinkos.So to set the record straight you should define it as derogatory.
Thank you for your feedback. I agree with tunaafi that pejorative covers this. However, I see that one of my colleagues has recently added 'offensive' to the usage on this, so that will appear alongside pejorative when the dictionary is updated. I hope that is satisfactory.