What does "tribal" mean? (serious question.)
It goes along with being hostile to outsiders. There was an "in group" inside the NBA GAF thread that consisted of regular posters in their thread.
Being a regular poster is not in itself bad, but it's bad when your "in group" develops its own rule set and becomes hostile to those they perceive as not part of their "in group." In turn, they become protective of those they see as their "brothers" and will stick up for them even to moderators, and even when those "brothers" are clearly being obnoxious or racist or whatever.
For instance, I permanently banned a prominent member of NHL GAF a couple of years ago for multiple, clear violations of our rules. When I did so, another member of NHL GAF sent me a PM and threatened me physically, suggesting he can easily figure out where I live.
That's the sort of attitude I'm talking about, although it's rarely that extreme. We don't look kindly on fraternal orders that stick up for each other no matter what or who denigrate perceived outsiders to their little club.