And in the same vein, Liberals show no hesitation in lambasting other people with markedly different values (such as central/southern U.S.) who they lump in as "the same culture" and so consider a valid target.
Not everyone values, or even claims to value, the idea that no culture or value system can be strictly preferable to another. From the perspective where such preferences can exist, there's nothing inconsistent about expressing one.
You're not wrong. Mocking country bumpkins has been our national past time, making the careers of H. L. Mencken and contemporaries.
Two major fronts in the modern culture wars started with industrialization (urbanization), and the south's remything their humiliating unconditional surrender and occupation in defense of slavery as some kind of Noble Lost Cause (victimhood).
As a proud urban progressive, I'm only too eager, happy to hail the wambulance for anyone railing against us job creators and fitness nuts. So I guess I'm no better.
Whether these places share a culture or not, they are dominated by a particular political culture that has an amplified impact due to a variety of factors.