Well I've lived in both cities so this is what I saw.
People in Dallas generally don't care about Houston teams one way or the other although I did have friends that had a rooting interest in the Rockets or Astros.
There are tons of Cowboy fans in the Houston area and that does rub the Houston people the wrong way; it has for years and it will continue to bother them.
Some of them even say as long as they beat the Cowboys their season was a success.
I prefer to be a smarter fan that that and root for my team to beat the teams not only in their own division but in their own conference.
But hey that's just me.