It's just so silly to me. The towel didn't go onto the court and hit a player, Hickson made the free throw, and the Celtics still had a lead of over 20 points. I can understand the league saying "don't do it again," and making an example out of him, but to actually fine him?!?!
During the Celtics-Heat series there was a moment in the Garden when Wyc Grousbeck was upset about a call or something that Jermaine O'Neal had done. He stood up from his seat underneath the basket, and nearly walked onto the court while talking trash to Jermaine O'Neal. I don't know if anyone else remembers this, but it was a really crazy moment. It's amazing to me that this would go unnoticed and be allowed by the league but that Ainge throwing a towel in the air would.
Distracting people during free throws is part of the game, and I have to imagine that this would have gone unnoticed if it had taken place in the Garden. I understand he's a GM, but I wouldn't have had a problem if an opposing team's GM had done that to us under the same circumstances.