I have to say, it depends on where you go. Some forums have worse PS3 fanboys, others have worse 360 fanboys etc... Gametrailers is an example of a community where PS3 fanboys are worse than 360 ones. Often you find people complaining about FFXIII going multiplatform and such.
As for the exclusivity arguement, I agree that often most games cannot be considered 360 exclusive. Although I will say that it can be a Microsoft exclusive if it's not also on a Mac. A bit like for example, the God Of War series is a Sony exclusive, but not a PS3 exclusive, since I believe it's on PS2 and PSP as well. But that's all semantics.
I agree on the whole though. Fanboys are peshaps the most damaging thing in the representation of the gaming world. I admittedly don't have a PSP or PS3, but I intend to own them both.
Hope you find other gaming communities a bit better (like this one for example).