I encounter this regularly when talking about operating systems, programming languages, text editors, and even non-technical things like car manufacturers, methods for making coffee, types of beer, music, politics, .... I never connected it with a "want to be part of the tribe" behavior. I wonder if this behavior is something that's relatively recent or dates back to primitive man. Regardless, it makes it difficult to discuss things in a rational, objective manner to understand what's really going on and the nuances involved.
Also on jgoerzen's blog entry is a link to "Why smart people defend bad ideas". Reading the two essays back to back was really funky.