Nonviolence doesn't just prohibit physical violence, but psychological violence (name-calling, isolation etc.)
Attitude towards your opponent: Do you see them as an enemy, or actively care for them?
Intent: Do you want to change an opponent's mind against their will (coercion) or win them to the other side (conversion)?
So there's 'tactical nonviolence', where people prohibit only physical violence but hold antagonism to opponents. The effectiveness of these actions are only limited to a few individuals or campaigns.
Gandhi's revolution was characterised by prohibiting both physical and psychological violence (which is why it's the most successful nonviolent movement in history).
Movements in America as a whole, are somewhere in between. This often leads to confusion and dissension with different strategies and tactics. By knowing where everyone stands, differences can be dealt with and possibly resolved