Hardly. You're just quibbling about loose language, not outlining a contradiction. What the author means is that the only way to stop the existing movements is

Hardly. You're just quibbling about loose language, not outlining a contradiction. What the author means is that the only way to stop the existing movements is by stopping their leaders. That will stop the movements, but it doesn't prevent other movements from rising in their stead. In fact, the author makes a very convincing case, argued over much more than two out-of-context sentences, that the way the system works at the moment makes it impossible for any principled leader to arise, since any time one does, criminal ganges will fund his opponents (presumably until he's dead) and perpetuate the "un-wars". This strongly implies that whilst killing the leaders might stop their respective movements, it won't stop the endless cycle.