I'd have to disagree with you here. "Community" covers a lot of ground, and even in a small town -- which would be a community by anyone's definition -- there's plenty of disagreement about everything except the geographical location and name of the town. And even there there's room for disagreement.

Similarly, it makes sense to talk about an LJ "community", the "filk community", the "Ubuntu user community", and so on while still allowing a wide range of views and beliefs. Again, such a community is defined by a web site, a musical genre, an operating system and its associated blogs, ... within which people who consider themselves part of the "community" interact.