I'm a longtime diehard fan of the 2 winter season teams and have had season tickets to both on occasion.
Philly fans are passionate but are not misunderstood. Constant fighting, especially at Eagles games. Fans routinely pissing in sinks or just going on the floor in the restroom. Belligerent towards opposing team's fans.
I've been to all 4 major sports all over the country and trust me- Philly fans behavior is special, and not in a good way.