There is no rationale for quitting "to protect the average". Bad rounds will be eliminated by good rounds eventually because only a certain no. of the best rounds will count.
To me it is a frustrated reaction of people who don't want to see a bad result and do not respect their opponents/competitors. It is unpleasant but human, and the provider will do nothing against those people supposedly because they also are paying customers.
It's a thing we cannot change, therefore it's better just to accept it than to become sick.
The best we can do is to avoid criitical situations (like skin games IMO) and to bring five minutes' time to wait after a disconnect in match play - the reward is a win in the statistic, and a "lose" for the quitter.