Running Up The Score

Is it right to run up the score on an opponent? Should a team ever be told by the coach they should not score points? Your team is ahead by a very large margin and the starters have been taken out of the game. Is it right to tell the subs not to score? Which is the worst scenario when your team is ahead by a very large margin: tell your team not to score more points? let the other team score but they know you are letting them score?