I used to run a website for many years concerning the Dave Matthews Band, which had a message board system ("old school" in comparison to this one) that had around 20,000 subscribers, roughly a few thousand of those who were considered "active users."
There came a point when discussions veered way off-course, having very little do to with the band or absolutely nothing at all. We termed it "nDMBc," or non-Dave Matthews Band content. On the one hand, I thought it hurt the solid discussion of things band-related. However, I also saw the value in having it as long as it was kept separate in some manner so that people coming to the site were not confused by the vast array of topics. We wanted to keep it easier for people to find discussions they would want to read or join in on.
We solved the problem first by having folks put a small "nDMBc" at the beginning of their topic of discussion, so a quick scan made it easy to determine what was relevant to those wanting to discuss the band and what wasn't directly on topic. Later, we found it best to create a separate category of discussion with the same name, given that it had grown to some popularity (including discussion on sports, politics, etc.). It actually became a worthwhile section to check out, given that we had some very cool, smart people who had some highly entertaining discussions.
I'm not sure if any of this offers a solution to what's happening here. I guess my point is that we were able to resolve the issue and everything came out positive in the long-term.