Welcome aboard, Erik.
For what it's worth, rivalries between special interest websites are fairly common, although the FRN is among the more extreme examples. You'll see rivalries among the highly competitive humor and social networking oriented sites as well, if you dig into the histories of reddit, Digg, StumbleUpon, Something Awful, YTMND, etc. Each community develops its own shibboleths and arcane practices to separate the true believers from the unhip n00bs and outsiders. There have been particularly intense rivalries between a couple of anonymous image boards. The rivalry was so intense that certain keywords were considered bannable offenses. Woe unto anyone who dared to quote a phrase or meme associated with the "enemy" site.
I've been active on a particular photography website since the 1990s and a moderator there for the past 10 years. Like any hobbyist or artistic website it too has its share of drama and rivalries. That's just the nature of creative folks who are passionate about their artistic pursuits. Within reasonable boundaries a competitive spirit and insider jargon can help form bonds that stabilize a community. Many of us participate on other photography websites and neither the members nor the administrators consider it a breach of loyalty, let alone treason. In fact crossover participation is usually mutually beneficial, and shared membership can help disseminate news and helpful techniques more efficiently.