Traitor or Whistle-blower?

The difference between a treasonous act and an act that will benefit society does not have a textbook answer. The film On the Waterfront explores that divide. Terry, a character in the movie who does not work for the tyrannical mob but is friendly with them, must decide whether to testify against the mob for the death of a boy who was pushed off the roof. While he is trying to decide, many people give him advice on how to act. His brother Charlie is part of the mob and believes that Terry's first duty is to his friends. By friends, he means the mob. Charlie thinks that you are ratting on your friends when you testify against them. On the other hand, the local priest knows that what the mob does is wrong and encourages Terry to testify against them. He knows that silence will not help the workers who cannot earn decent wages because of the mob, and so the mob needs to be taken down. The priest thinks that you are not committing treason when you are acting against your friends and family for the greater good of the society. In the end, Terry decides that he must end the injustice even if he might have to sacrifice himself to do so.
I believe that a traitor is only someone who does something for selfish reasons. If they are doing it for the greater good of the society, then it is excusable. Even if you are selling out on your friends, if it will drastically improve the community's well-being then it is alright. For example, if you have a friend that you know has been stealing iPods, then it would be much better to turn them in and keep them from continuing t0 anger those who they have stolen from and progressing to worse thefts. You are genuinely helping society. However, if you simply want to see you friend get into trouble, then you are ratting your friend out.