On The Waterfront: Whistleblower vs. Stool Pigeon

In the movie, "On The Waterfront", the dockworkers are rendered helpless by the "powerful" mob. They have power only because they use fear and force to hurt those who speak out or challenge their authority in any way. Their leader, Johnny Friendly, is very corrupted. His "second in command" is Charlie, Terry's older brother. To them, and to everyone else who is in with the mob, someone who speaks up is a "stool pigeon". They could not afford for even one person to stand up for what they believe is right because it would lead to the end of their existence. I believe that this is because they know what they are doing is wrong in society's mind. To those who cannot be influenced by the mob, like Edy and her father, the priest, Doogan, and Joey, standing up to the mob would be considered a noble deed. Every worker knows that what is being done to them is unfair, yet they feel as though they can do nothing. They know that Johnny Friendly would take his revenge and have them killed one way or another. A person who dared go through with their intentions and stand up for the dockworkers would be a brave and courageous person. Terry is on the fence for most of the movie and has trouble deciding where stands on the issue. However, once his brother Charlie is killed, he decides that he has to stand up to the mob and Johnny Friendly no matter what the consequence.
I believe a stool pigeon or a tattletale is someone who tells on others for a personal gain of some sort. They might do it as revenge or to advance their own personal causes somehow. These type of people in my mind are "bad" and do not have a good sense of what is right and wrong. On the otherhand, I believe that a whistleblower or ethical crusader is someone who risks some personal aspect of their own life, be it safety, reputation, etc., to stand up for what they believe in. They sacrifice something of their own for the benefit of a larger whole, in this case, the dockworkers. I believe that speaking out about what you believe in is always okay with one exception. If your motives are not pure, meaning you are doing something for the benefit of a small group of people or even just yourself, it is wrong. With that said, I believe it that if you know something wrong is going on and yet you do nothing about it because you don't want to put yourself out there and take a risk, you are equally to blame as someone with the wrong motives. Both types of people are selfish and to be named as a whistleblower, being selfless is key.