The Constitution was amended to explicitly prohibit Congress from making laws abridging the freedom of speech as well.
What's relevant is the Supreme Court reconsidering a previous decision without any change to the Constitution, but that too has happened before, e.g. Brown v. Board of Education.
We have a comment complaining about the Court reading beyond what’s written, and another complaining about them failing to do so. I’m just pointing out the inconsistency. If you want total free speech based on a plain reading of the first amendment without considering context, then there’s no reasonable way for the Court to find slavery to be unconstitutional prior to the 13th amendment.
I’m not taking a position here, just pointing out the implications of the slavery thing.
What's relevant is the Supreme Court reconsidering a previous decision without any change to the Constitution, but that too has happened before, e.g. Brown v. Board of Education.