What's with this Yankees Suck thing in Boston

I have been in Boston for a while. We came here from Vermont by way of Marin County in Northern California. I have been in every state in The Union. It has been my experience that the New York Yankees are not well liked in "the rest" of the country.
However, in Boston it has become a mania, if not a disease to hate the Bronx Bombers.
There are "YANKEES SUCK" bumper stickers, signs, even tattoos at the part of a woman's back that should be covered by their jeans but it not.
I have been part of several conversations in Boston where it was explained to me why the Yankees are in this condition.
None of them seem to have anything to do with the Yankees themselves. It has to do with the way Boston feels about how their American League team, the Red Sox are always bested by them in the Pennant Race. It seems for many years, the Red Sox have come in second. Not since near the end of the Great War in Europe, that being called WWI around here, have the Boston Red Sox surpassed the Yankees in the World Series.
The obvious solution is to move the teams into two different competing areas. That way they won't loose their "edge" by having to constantly look up from the road and see a pin striped behind trudging ahead of them.
The kicker of this mania manifested itself at the celebration of the first Superbowl win of the New England Patriots in Boston. One of the team mates, holding the trophy got up to speak to the crowd, to thank them for their support and promise another trophy in the near future. All he could say was "YANKEES SUCK!"
The two teams don't even play in the same sport! The crowd reflexively roared in response for a moment or two. They then realized this had nothing to do with what they were there to celebrate and went on with the business of mob celebratory behavior.
If you expected something about the Yankees winning so many world series, pennants and all of the other baseball related trophies, it's a beaten path and there is always Google to get the facts, or as they are related on the Intenet.