I wonder sometimes if its the writer/viewer's inability to see past the solid characteristics the guys had at the start of the series. Sam was super anti-John, so a Sam fan who doesn't grow with the character will always treat John like a pariah. Dean was super pro-John, so a Dean fan who doesn't grow with the character...yadda.

I'm not talking huge sects of fans, I hope, but it's gotta exist out there.