As a man, if a friend is kicking my ass at tennis or racquetball (which happens...I can beat some of my friends, others it's an aberration when I beat them, but great workout either way), nothing irritates me more than sensing that he's deliberately letting up on me. By all means, if you can beat me 15-0 then do it. I don't want any cheap points and it doesn't make me feel better at all if the final margin is closer because he took it easy. I think that's the most emasculating thing he could do.
"Running up the score" is unsportsmanlike when it's kids playing. Not when it's professionals. If you're a pro, have some damn self-respect and stop the other guy or die trying. It was stupid when people criticized New England for this, and it's stupid for those who have criticized us for it today too.