The problem with peaceful protests are the people they are protesting against aren't usually peaceful.
In a Utopian world full of compassionate and empathetic people, peaceful protects would be great. But not in our world, not yet anyway. The good news is people at large are indeed getting less violent over time.
Well that's the problem with the government then, most of the time they won't listen as long as they can have what they want. That's why politics were referred as the devil's playground.