Silence can be an effective tool.

It can be but you have to use it in the right way.
Nothing demonstrates anger or how upset you are better than silence.

But you have to be prepared to give information to those who ask about the why.

Otherwise people, especially in groups, will disregard your feelings and chalk it up to you being 'moody' and them getting their own way.

Silence can be violent sort of like slit wrist- zack de la rocha