I have met classy Philly fans. They aren't that uncommon in my experience, in fact. However, I still think that there's an extremely unhealthy general attitude among Philadelphia fans that just isn't matched anywhere else.
My favorite Philly story is about Gus Zernial, outfielder for the Athletics in 1954 just before the team moved to Kansas City. Zernial was a power hitter, had hit 42 homers for the team the year before, and had driven in 100 runs for the previous three seasons. But he was banged up in the team's last year in Philly and didn't play that much or that well. Philly fans made him a punching bag for their frustration over the team not being good and their impending move.
In the final game of the year, Zernial tripped over a sprinkler in the outfield and broke his shoulder. As he writhed in pain, the fans booed. Despite the pain, Zernial said that as he lay there with the boos washing over him he only had one thought: "Thank God I don't have to come here anymore."
Yeah, that's 50+ years ago. Very little to suggest things have changed all that much in a couple of generations.