Yeah, Eagles are the Buffalo Bills of the NFC. Next? We both have the same amount of NFC championships in the last 10 years
Your basis for comparisons is confusing.
The Bills have had one winning season in the last decade.and haven't made the playoffs this century yet they have had a fairly loyal fanbase because it's Buffalo and the Bills are all they know but even that fansbase looks to be done supporting them now. The Eagles have been playoff bound almost all of those years. I guess I am not understanding your comparisons to the Bills and Panthers as teams or fanbases because they are nothing alike and can't be compared. Just because the Panthers and Eagles have 1 NFC championship each in the last decade doesn't mean the fanbases will be the same.
The Eagles fanbase is "rabid" because they have been consistantly making the playoffs and the last 10 years or so and they have been relatively exciting and promising. The Bills and the Panthers have not but if you think they (Eagles fanbase) supported the team when the things were even slightly down, you are mistaken.