Pretty much, it's an ego thing. People get a "rush" about proving somebody wrong and "winning" a fight. It's usually less about learning about something or trying to determine what's right and more about trying to prove somebody wrong so you can look smart. 

There's a reason I don't really feel like jumping into massive, multi-quoted passive aggressive to slanderous debates/arguments/e-peen stroking fests for the most part. Whereas I mainly like to talk about things, get educated about something I want to know more about, or put in my two bits about something that I am certain is factually correct when I see something that's wrong (like, actual facts, not something subjective like say if God exists, the ethics of suicide or anything like that). Of course, I like anyone get sucked into things from time to time, but I don't exactly go seeking it out or deriving some kind of pleasure with arguing over something that's almost certain to not reach a mutually respective conclusion where both parties feel satisfied with the discourse. Most of the threads you see in Off-Topic that are pages upon pages and hundreds of posts usually go completely off the original topic as somebody's trying to illustrate an idea to prove their own position, and then it escalates when somebody else counters the tangent with something else and blah blah blah. In short, it's less about learning and more about "winning".

If you can ever call being a part of an internet slap fight that.