Do people really actually like underdogs?

Yesterday's games really underscored something for me. People don't really want to pull for the little guy in the NFL. I have two specific examples that make me think this. First, think of the Seattle Seahawks who won the NFC West and are decidedly the underdogs in these playoffs, then think of the Indianapolis Colts against the New York Jets.
Ever since it was learned that the Seahawks were going to be in the playoffs, gnashing of teeth and lamentations abound at the idea that a 7-9 team was going to make the playoffs. They won their conference, they represent the NFC West, but they did what was required of them by the rules of the game to make the post season. They ended up playing last year's Super Bowl Champion on Wild Card weekend, the definition of an underdog. When the Seahawks won, the airwaves weren't filled with plaudits for the winners, but rather outcry and the near unanimous declaration that changes should prevent something like this from ever happening again.
The Colts/Jets game is another story. For whatever reason, the Twins are still the little guy that most people outside of the AL Central like, but for whatever reason Indianapolis has earned the scorn of many in the league. Purveyors of NFL related hate, Kissing Suzy Kolber, are among the most anti-Colts sites out there, and they simply can't put a good label on the rationale. In most other walks of life, Indianapolis the city is barely a blip on the radar of the East Ciast, and New York teams (and fans) are typically the ones thought of as overbearing and unlikable, but no, when the Jets won last night, everyone seemed happy with that result (outside of Colts fans like me, of course).
The NFL is the only sport I can think of where this applies. It doesn't even apply in college football, where the popular opinion is that Boise State and TCU deserve shots at the title. Why is the NFL different?