Quitter, Sandbaggers and sore losers will always exist. Yes, they suck and all can ruin a good game for you. Some players are more concerned about winning and stats than finishing what they've started; a juvenile perspective on their part. If they'd stick around and finish the game the outcome is not always what they "predict" after a bad shot. I've completely fubar'd a shot or two and lost the hole only to have my opponent do the same thing a hole or two later. More often than not, this usually is the case.
My two cents... once you've identified a quitter don't even humor them the next time you run into them. I keep a list of the quitters and sore losers I've come across and I avoid them. Consequently, some have apologized, after being cancelled numerous times, and have proven themselves accordingly. Granted, this is rare but it does happen once your point is driven home.
Best of luck!
-Steel