Now don't get me wrong, I have nothing against peaceful protesting. Many times it works out and you get what you need out of it.
However, many people use it as an excuse to be lazy. They decide that protesting is all they need to do to get what they want.
That's not true. To get what you want or need your going to have to get off your lazy butt and do something about it. If your protesting cutting down trees (for example) then do more then just protest it. Plant extra trees around your neighborhood (with permission where needed), get a petition started, find out the facts.
And most of all; THINK! Why does protesting always have to end up in violence. All your doing then is showing the world that you don't really care for the topic, you just want to break stuff. In the end your only hurting yourself.
If you really care for something, then do something about it. And don't participate in stuff that could potentially hurt yourself, others or your topic.