Violence is never the preferred way to go and sometimes things can be attained without it. However, we human beings do not easily cede the power we have, and if change is to happen, it will often be put off until a group of people decides that they are willing to stir things up.
I think violence is only to be used as a last resort in an effort to change things, I think throughout history we have seen violence used to overthrow a Government and the new Government is just as bad as the only Government, I think the best way to make change happen is through the power of voting.
It is my opinion that violence is not actually necessary in order to change things. Whether the change be big or small, the goal can be accomplished through proper communication and discussion. Unity and compromise can be much more effective and efficient than violence in inciting change. Violence is not necessary.
No, violence is not necessary in order to change things, because beliefs and good arguments can change things too. The USSR collapsed without any violence. That was a change that happened because of economic forces. Changes on a smaller scale can come with electing new leaders, such as when the US turned socialist by electing President Obama.
I think there can be power in numbers if there are enough numbers. And, of course, this varies depending on the circumstances. Sometimes violence is necessary. An obvious example is Nazi Germany. They had to be stopped or else the entire world would have been in trouble. But it can usually be handled peacefully.