""if each person thinks they are right, then there's not much point in discussion beyond simply announcing one's position.""

People have said that many times, in MC, for example. Regardless, people still post and answer each other in pointless argument. This leads to much of the discord. It seems the desire to be right, win, and be seen right is very strong. Also, the desire to "put the other person in their place", is also strong. This is encouraged by similar minded people weighing in on one side or the other. The religious posts, and middle east threads, where strong personal views
exist are good examples.