There’s an Evil Empire ™ in each of the four major US sports that I always root against:
NFL - Dallas Cowboys. The audacity to call themselves “America’s Team;” Jerry Jones’ arrogance; the unqualified amount of attention they receive from the MSM, from their being perennial NFC favorites despite showing no real reason to be considered so, to the intense scrutiny when they fail to meet those unrealistic expectations.
NHL - Detroit Red Wings. The audacity to call themselves “Hockeytown;” Mike Babcock’s smug, self-righteous, beady-eyed face; the amount of love Datsyuk and Lidstrom (and Yzerman in the past) receive–yeah, they’re great players, shut up about it already; they get schlubs like Chris Osgood championship rings.
MLB - New York Yankees. I don’t even follow baseball, but I always root against them and I don’t think that should require an explanation.
NBA - Los Angeles Lakers. I follow basketball even less than I follow baseball, and this one, admittedly, stems almost entirely from my experience with Lakers fans when I lived in Southern California, though part of it is also due to an innate dislike of all things Kobe Bryant.
Outside of those four:
Philadelphia Flyers – Never has there been a more consistently dirty team. Fans cry about their undeserved reputation, and then defend the acquisition of guys like Pronger and Emery and Asham, the hits of guys like Mike Richards and the antics of guys like Daniel Carcillo.
Sean Avery – World Class Douche and all-around unlikeable guy.
Sidney Crosby – I probably wouldn’t mind him so much if I didn’t have to hear about him all the freaking time. Also, his mustache is pathetic. Also, Crosby apologists are among the most annoying people on the planet.
Alexander Ovechkin – Same issue as with Crosby–all the hype, plus the manufactured feud between the two–but also because he’s a reckless ogre cited as the greatest player in the game by fans and the media alike when they’re not defending his knee-to-knee hits, blatant charges and other generally borderline dirty play.
I’ve come to the conclusion that my dislike/hatred of teams and/or players (and thus what makes them villainous in my mind) is very heavily influenced by my level of interaction with their fans/supporters and my perception of their behavior, or else how much press they get (deservedly or not).