Yeah. Tell that to Debs:
Debs v. United States (1919)
"Eugene V. Debs, a well known socialist, gave a public speech to an assembly of people in Canton, Ohio. The speech was about the growth of socialism and contained statements which were intended to interfere with recruiting and advocated insubordination, disloyalty, and mutiny in the armed forces. Debs was arrested and charged with violating the Espionage Act of 1917. At issue was whether the United States violated the right of freedom of speech given to Debs in the First Amendment of the United States Constitution.
"The Supreme Court of the United States upheld the lower court's decision in favor of the United States. The Court said that Debs had actually planned to discourage people from enlisting in the Armed Forces. The Court refused to grant him protection under the First Amendment freedom of speech clause, stating that Debs "used words [in his speech] with the purpose of obstructing the recruiting service." Debs' conviction under the Espionage Act would stand, because his speech represented a "clear and present danger" to the safety of the United States."
Your Warren Court era example would not have passed the smell test circa 1863. Interesting, though, that you would highlight a Klan case.
Debs wasn't around until many years after the events we are discussing.