New York has New Jersey. That's the place New Yorkers like to hate on most. Why? I don't know. New Jersey really ain't all that bad. It's definitely not as good as New York, but it seems like a pretty decent place to live.
Oklahoma, on the other hand, is actually the worst place in the world. It's just north of Texas and it's the source of well-deserved mockery. Texans hate Oklahoma because it's horrible. Upon entering Oklahoma, your body contorts and a truly visceral, supernatural hate overwhelms your mind. Sometimes you just vomit like in The Exorcist.
Oklahoma is the worst because it is a manifestation of all the silly stereotypes outsiders have about Texas. Oklahoma, no one likes you.