I guess I'm just surrounded by a different atmosphere as I know plenty of people who are rabid about one of the teams (though you're right, not both). Also, 20% of 20 million people equals a lot more people than currently reside in Buffalo.
It's hard to compare I suppose. In Buffalo the team lives in a fishbowl with most of the population peering in. It might be easier to hide in NYC, but even hidden there are a lot more people critical of the teams than in Buffalo.