As an Oiler fan, I used to loathe the Cowboys, but I actually worked for the Cowboys organization for 2 summers and still maintain a relationship with a few people there (including a few executives). So, my pure loathing has cooled into just a general dislike for the team. An upgrade as far as Cowboys fans are concerned...
In the late 70s and early 80s the cops here gave away cowboy cards, I always wanted to get Oilers cards, but they never made them, just one more reason. (Does anyone remeber those?) They did it in the 90s also, but I think the called them wanted posters.
I primarily just hate Dallas. That hate grew into a natural hatred for the Cowboys, because well, that's how that wretched city identifies itself. When the Oilers left, I didn't hate the Cowboys so much. Just the city itself. The interesting thing for me is that I've been fortunate to travel the world many times over and I know or have known many people from abroad who have dealings in Texas. They ALL hate Dallas. These are people from Europe who don't give a damn about American football. They simply can't stand Dallas because of the people. Not "Cowboys fans," just the people of Dallas itself. I've heard the words 'self-centered,' 'obnoxious,' 'rude,' and 'fake'....the list goes on from natives of Great Britain to Sicily. Its even been taken to the point where I've actually stood up for the people of Dallas, telling those abroad who were so offended that they "must've just met Cowboys fans." All of these people LOVE Houston. They refer to the people here as 'friendly' and 'genuine,' and always have something to say about the downright awful press Houston gets both nationally and abroad. F*ck Dallas. Oh, here's a trivia factoid: Houston, Texas was named after a genuine Texas hero. Dallas was named after some yankee politician no one has ever heard of.
My experience has been the same. Interesting you say that, because I was talking about this with a friend yesterday. He's from Colorado and said when he came to Texas, he had a stereotype of Texans that he didn't like. He found it not to be true when he came to Houston. He's since spent some time in Dallas and found that stereotype to be entirely true up there.