Generally it does seem to be a common attribute. Some activists are also idealists, which is to say they have a view of the world that is idealized based on their principles which is a distortion of reality to a lesser or greater extent.

Living as I do in the San Francisco bay area, I encounter all forms of activists from people living in trees on college campuses (illegally) to folks who provide services to undocumented workers, to folks who expose security flaws on web sites. Of the ones with whom I've been able to talk briefly about their goals, all of them did not grasp that the results of activism are later perceived through the dialog of what the people that 'win' write. (sort of a variation on the winners write the history)