Nobody at the time called Hollywood blacklisting a First Amendment violation. In fact, the First Amendment offered pretty weak protections for content once deemed pretty subversive, yet considered banal today, until the 1969 Brandenberg Supreme Court decision. For example, in the 1920s you could be criminally prosecuted for openly sympathizing with the Communist party and that was deemed just fine. See Whitney v. California, 274 U.S. 357 (1927).

It shouldn’t be lost on anyone knowledgeable of legal history that every conservative who relies on modern “free speech” principles to insulate themselves from liability for disseminating bullshit to achieve their political gains has a “liberal activist court” to thank for the privilege.