Well, there are LA: http://nypost.com/2015/10/13/mets-fan-victim-of-bloody-dodger-stadium-beatdown/
St. Louis, where their own fans have shot each other and beat down cubs fans.
Jets fans, where their most famous fan Fireman Ed is beloved for being a violent trash talker.
I've been to a lot of Philly sports events and there are plenty of chuckle heads, but I've seen just as bad with Bills and Sabres fans. But no the Santa Snowball incident, 20 years before I was born, still gets brought up.