If the world were like your post, it isn't, nor is it in terms of Cowboy fans I can tell you, but if it were, then you should ask yourself which side you think is the more logical from a sports perspective. Houston fans are like everybody else in the country.
Giants-Jets, Eagles-Steelers, Bear-Packers (state line notwithstanding), Niners-Raiders, Bucs-Dolphins (I assume), all of these have it right in my book, they hate each other. It has nothing to do with this BS state loyalty I keep hearing about, that's a crock. Nor does it have anything to do with jealousy (Cowboy fans) or potty training (those of you that think this is some sort of fault). It's actually completely natural.
Since I was old enough to be a sports fan, we'll call it 40 years, I have despised other teams in the state, only pulling for them in certain playoff scenarios or special circumstances such as some college football games and who they are playing. Virtually all of the people I have ever known feel the same way. Those that lie and say they don't show their true colors when it's 19-10 with no time left. That's where you see the lie.
I'm an ___A___ fan, therefore I especially dislike ___B____.
A. Astros....B. Rangers
A. Texans....B. Cowboys
A. Rockets....B. Spurs, Mavericks
A. Stars.....B. (don't care, it's just Dallas)
Inferiority complex, please. I can tell you that is not the case here. Talk about a tired argument. It's actually possible to simply dislike another team for a host of other reasons.