You can't have your cake and eat it. If speech doesn't have power over people, why do authoritarian governments fear it and seek to curtail that freedom?
Speech can motivate, encourage, inspire, disgust, leave indifferent, irritate, and so on -- but people who act on a given idea do it of their own free will. What authoritarian government fears is that people use their independent minds, allow disagreement and debate, and choose to act in defense of their freedoms.