This isn't a topic I'm posting as a result of our 1st league games, but is something that has always been important to me. I have won and, yes lost my share of matches. I have argued a ref's decision on numerous occasions. I know how difficult it can be to control your emotions when you've physically exerted yourself to such a high degree and are willing to do anything to win. Often it can be more difficult without a ref, and even more so if you're opponent is an unfair player. People like this have trouble getting matches and for good reason. If playing squash with someone isn't enjoyable, then don't play them. In tournaments we can't avoid this, but we can still do our part and play fair.
If you have any issue with a ref's call, I think it's fine to ask for clarification, or even to talk to them about it between games (although you would be better served refocusing for the next game). But never show up a ref or make them look stupid. They are doing us all a favour by reffing and are trying their best.
Just as important is to call your shots down/out when appropriate (and yes give your opponent a stroke when deserved, refs make mistakes too!), give your opponent every opportunity to get to the ball, and don't swear or throw your racquet. Not only does this set bad examples for the viewers (especially the juniors), and nobody will be talking about your win, just about what a jerk you were. It's much harder to handle losing, but this shows our true colours and character. Don't make up excuses (true or imagined) if you lose, just admit your opponent outplayed you and was better that day.
Roger Federer is a perfect example for us all. He's a great champion, but is just as graceful in defeat. And afterall, the better player usually wins. So train hard, play hard, play to win, play fair, congratulate your opponent if they beat you and be sure to thank the ref after the match.