Why would there be any doubt that if the hypothetical constitutional provision existed, they would have used it as an enemies list? Remember that they added, for example, green activists and advocates of non-violence on terrorist watchlists after 9-11. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
"advocacy of violent overthrow of the government" is a good phrase to google.
From Yates:
"[T]hat indoctrination of a group in preparation for future violent action, as well as exhortation to immediate action, by advocacy found to be directed to "action for the accomplishment" of forcible overthrow, [directed] to violence "as a rule or principle of action," and employing "language of incitement," ... is not constitutionally protected when the group is of sufficient size and cohesiveness, is sufficiently oriented towards action, and other circumstances are such as reasonably to justify apprehension that action will occur. (p. 321)"
http://www.answers.com/topic/yates-v-united-states Align culture with our nature.
