The phenomenon is very similar to infighting in a boxing match (boxing closer to an opponent than at arm's length). Neither opponent is at a good distance to get in a good, clean punch, and the match quickly gets boring. That's why the referees break up infighting and make the opponents start again at a distance.
Closing a thread is not the end of the world - it's just giving everybody a chance to make a new start on a rational basis.
-Joe-