It means many things, most of the time all rolled into one...
Say in the case of the Texans and the Saints, If an ubiased ESPN/whatever commentator says it, then his opinion is probably that the Saints "are" a Super Bowl contender and that the Texans are "not"... He may also believe the Texans will play with more passion because of who they are playing...
But say a Saints fan says it, yah, it will be an "excuse", and sometimes an "insult" shot at the Texans, but in all honesty most of it is probably related to their belief that their team is the best and everyone wants to beat them and will play their best against them...