I think this is a very good point. Every action that is effective is so because of leverage. Without leverage, you have no position of power to demand action of another.
Boycotts, therefore, can only be effective if there is a significant number of people who will commit to be faithful to the boycott and ensure and adverse effect on whom they are protesting.
Likewise, protests without some sort of leverage will not be effective. Leverage can be gained in the form of media coverage that then reflects poorly on the protested and could effect a change. But, without some sort of leverage...like threat of violence...protests are a waste of time.