It's fun to discuss things and find out why tf people think what they think. Most people have really not thought through their opinions at all, or are really bad at expressing them. But it's more than just that, it's interesting to see how people behave and react, the way that they express their argument, how they deal with challenges, and especially having their opinion disagreed with in public.
Not to long ago I talked to a guy that was really angry at me and always flaming me calling me a moron and saying everything I said was wrong. Anyway once I actually talked to him it turns out he actually agreed with everything I said, but he was just really really bad at communicating and he was one of those people who think it's 'cool' to flame constantly.
He would say things like "moron, all games are single threaded" then I talked to him and he admits "ok, you are right, for the last 20+ years all games are multithreaded, but single threaded performance is more important". It was like that for a list of maybe 10 objections that he had flamed me over. Every one he would admit "ok, you are right", but he would never admit it in public and would always flame me behind my back because of his ego and "I'm an asshole and a bigot, deal with it" tough boy attitude.
I remember a long time ago people like Odlov or Mister616 or Hyde, plus the "3 Unholy Tyrants" (just made that name up) - Juntalis, Vox, and BP, and also people who rarely post but when they do it's fun (eg hanz0), they would always be good fun. Now days we have Ele, Zelda, Oracle, hawkes, ynvaser, etc. Lots of good guys to have fun with. Though there are also some randoms who are enthusiastic about random topics too.
So in summary, mainly just good banter.