The relationship between Yankee and Redsox fans is a lot more hatefull on the Redsox side of the fence.
I've been to Yankee/Redsox games in both NY and Boston. The Yankee fans get pumped to play the Redsox. That's about it. I would say that there hasn't been a genuine hatred towards the Sox since the late 70s. However, in Boston, you almost get the sense that they hate the Yankees more than they love the BoSox.
The other odd thing I've noticed about this rivalry is the lack of a decided home field advantage for the Sox. If you go to a Yanks/Sox game at Yankee stadium, you get about 50,000 Yankee fans and 5,00 Sox fans. At Fenway you get about 20,000 Sox fans and 11,000 Yankee fans.
Last time I went to Fenway, there were 10 Yankee fans calling into question the sexuality of every great Boston athlete (after a Yankee win). I was expecting all hell to break lose. However, nothing happened. Had the reverse happened in NY, those Sox fans would have never made it out of the Bronx. Apparently Sox fans are more laid back.
GZ