The inherent buoyancy of New York City may normally be sufficient enough to carry a mediocre football team into the playoffs.  However, since the Giants are actually from Jersey, the confidence becomes tempered into a sluggish stupidity that ultimately and consistently ends up failing their fans.  The result of which are the most fair-weather and least respected fans in the league. 
HOW TO IDENTIFY THEM:  Sitting at a bar, not looking at each other and succinctly regurgitating the analysis from that morning’s Mike and the Mad Dog while complaining about every player’s performance.