Like it or not, people associate themselves with things, places and people as an intended reflection of their own attributes.
I have a friend who uses the first person plural when referring to the football team he supports, regardless of the fact that his contribution to their success is miniscule and indirect (despite his misgivings about ticket prices). He follows a team by choice, but his moods are then affected by their successes and failures. Superficially, this appears to be irrational, but it's a psychological consequence of his chosen association.
We are gregarious creatures, and almost all of us will associate with one tribe or another. For some people that is their home town. I don't see the big deal. This only becomes a problem (for me) if someone's zeal for their tribe causes them to mistreat people who they feel don't belong to that same tribe. In extreme cases this is expressed as racism and xenophobia, but it is more often not so harmful.