It is exactly what our country is built upon, that is assuming the people that are doing this are educated on the issues and not just causing a nuisance because they have nothing better to do. Also they better not get in the way or cause problems for citizens who aren't involved like the idiots who blocked I94 in minnesota last fall.
As Ghandi and Thouroux taught us, authority tends to become stultified and oppressive when unchallenged for too long. The best way to overcome the oppression of overbearing authority, whether such oppression is intended or not, is to publicly call authority to account. Authority's acts must be made public and held accountable by the public for only then will authority be responsive.
While rioting in protest to controversial issues accomplishes little, non-violent civil disobedience is a much better solution. Today's American government has become far too swayed by moneyed interests, so those who choose to take a stand in a very public way through defiant actions help bring this discussion into the public eye.
Yes, acts of non-violence defiance of the law are great protests. This was proven when Ghandi marched to make his own salt, in defiance of the British Empire in India, sparking popular support for independence. This worked when Martin Luther King, Jr. took his example and led by it himself, showing strength of resolve while turning the other cheek, even when that cheek was being hit with a police baton. Violence frightens and hurts people, it doesn't change anyone's mind. Civil disobedience allows people to truly think, then talk about, and then change the issues.