To my knowledge, the reason why free speech is held in such high regard is the idea that only citizens who are well-informed and have equal access to all argume

To my knowledge, the reason why free speech is held in such high regard is the idea that only citizens who are well-informed and have equal access to all arguments can make reasonable decisions - which is what a democracy rests on. If that is the reason though, I'd doubt that speech that deliberately attempts to subvert rational thought and manipulate the audience would fall under that protection.