Is there a distinction between advocacy and indoctrination preparatory to action?

These statements, individually and collectively, are "that sort of advocacy which, even though uttered with the hope that it may ultimately lead to violent revolution, is too remote from concrete action to be regarded as the kind of indoctrination preparatory to action which was condemned in Dennis. As one of the concurring opinions in Dennis put it: `Throughout our decisions there has recurred a distinction between the statement of an idea which may prompt its hearers to take unlawful action, and advocacy that such action be taken.' * * * The essential distinction is that those to whom the advocacy is addressed must be urged to do something, now or in the future, rather than merely to believe in something." Yates v. United States, supra, 77 S.Ct. 1064, 1078, 1080.