As a Boston fan it's pretty easy to be obnoxious considering our decade of dominance. I'm guilty of it myself and I have no shame about it. Although I must admit it's kinda hard to tell who the bandwagon fans are because our teams have won so much that it's easy to say "I've been a Boston fan for 10 years now!" when some people don't realize our teams were borderline-terrible the decade before. It doesn't surprise me that my wonderful city's name popped up a few times in this thread. Most people who are anti-Boston are just jealous haters.
I think it's nearly unanimous that Philly fans are the worst. It's mind-boggling that they are so obnoxious when their teams have won basically nothing, ever. Even the Phillies, who recently won a world series, are still the only pro sports team with 10,000 losses. That's 100 seasons of 100+ losses.
It's called Red Sox Nation for a reason. Sox fans regularly outnumber other fans during away games, most notably in places like Tampa and Baltimore. Speaking of which, Florida sports fans are also pretty bad. Every time I see someone in a Rays hat I think to myself, that was a wise purchase you made during the one month you rooted for the Rays. The Heat fans are even worse, they didn't even sell out their first-round playoff games. The Marlins stadium is empty all the time and the Dolphins would be in the same boat if they played more than 16 games a year.
The Sox may have a very high payroll in recent years but it's still significantly lower than the Yankees'. It's pretty easy to have a high payroll when you're in the middle of the MLB record for most consecutive ticket sellouts. And if you really think that's the only reason why Sox fans dislike the Yankees then you really are just a hater.