I thought of sports too. I personally have irrational hatred for rival players that, for example, accidental injured a player on my team in a big game. But it's almost like a joke or game; if I met the player in person I wouldn't act crazy.

I think the compartmentalizing you mentioned is interesting. In American politics right now, the home team and rivalry mentality seems to have spilled out into actually important areas of discourse. At the same time, neighbors still live in relative harmony in their day to day lives.

I just wonder if PG's theory really is more about trolls, despite him specifically addressing the distinction.