hmm, I did this one for a school debate (wasn't able to do the debate itself, but prepared a team)
Sports stars are NOT being overpaid. When you hear of David Beckham getting huge amounts of money, this is because the current club is willing to pay him that much.
You see, to sports teams, a player is an investment, not an employee. They purchase them to make their team win, not just to play. Think stockmarket, and you've got the idea. The more chance a player has to win a game for a team, the more that player is worth.
If, for example, the best player is 'up for sale', he(or she) will be worth much, much more than the new player who has just begun playing professionally.
which comes to my second point. Sports players are professionals. They are paid for what they do. In a business, the higher ranked an individual, the more they're paid, i.e. the CEO, who is more important to the company than its thousands of workers, will receive a much higher pay. Same in sports. The goalie who stops 2 goals is less important to the team than the player who kicks 3 goals for the team and wins the game.
Finally, the effect that would be had ON THE FANS if sports stars were paid less. The players are now expecting to be paid more, and most likely would not settle for less. "If our money goes, we go!"