Good for you, Rongotai. I always try to behave as you do. I don't always succeed! However, when I do, my experience echoes yours.
And if people think that dealing with grumpy, sullen or simply overstressed staff is reason enough to scream insults and oscenities, start fist fights, trash the place, endanger the safety of everyone around them, or simple beat and stab people half to death with broken vodka bottles perhaps they also ought to stay out of almost all fast food joints, all trains, many supermarkets, etc. etc. etc....