I'm fairly new to the game. I was a golf pro for many years and became a high school English teacher last year. Assistant tennis coach was attached to the job and I started playing with my players and fell in love with the game. This aspect of the game has been pretty difficult for me. I played my first tournament as a 3.5 and won my first match and was in a tight second. My opponent made some pretty objectionable calls that I thought were awfully close, but I couldn't tell for sure (although EVERY one happened to be out!). But I practiced what I always preach to my players, don't whine about it and move on. However it boiled over when I was serving. I hit a serve down the center line that was so clearly in that there is no way he could have missed it. He called it wide and I defiantly finally said Dude, that ball was in by 2 inches. It didn't even touch line. I saw a lot of court between the ball and the line. He replied that he saw it and it was out. I started walking toward the net and told him that I was looking right down the line and it was not even close, the ball was in and that there is no way that if he saw it he could have seen it as out. He immediately suggested we replay the point which we did.
After experiencing it myself, I now tell my players that if they are sure of a call, stand their ground and don't bother with the "are you sure" garbage. Tell them that you saw that it was in and ask the opponent to be more aware of their calls. If that doesn't work, get someone over to call lines and then you don't have to worry about it. I think that we as tennis players put up with the hookers a little too much. This is hard for me because I live by the creed that if I think a ball is close, I call it in.