Earlier quoted context omitted.
I don't think it'd hold up, but one could argue that the first amendment was an amendment, and thus changed the constitution, and therefore removed that ability of congress.
The amendments protect the rights as they existed at the time the amendment was passed. I.e. how would the plain text of the text be interpreted by a reasonable person in 1791. E.g., re 2nd, what did militia mean? Thus, the 1A locks in speech rights as they existed in 1791. Because there was no right to slander, or threaten, or commit treason, or "share" in 1791, Congress retained the power to regulate.
You seem to have a fundamental misunderstanding of the purpose and intentions of the constitution. Slander and fighting words are exceptions to the first amendment that were determined through the legislative process.
Essentially the entire US constitution is negative rights - the right to X when X means government NOT doing something. Right to freedom of movement, right to freedom of religion, right to freedom of speech, right to privacy - these are restrictions on government to protect the liberties of the people. And then you come to the tenth amendment -
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
It seems abundantly clear from even a cursory analysis that the founders explicitly designed the constitution to limit and restrict the power of a centralized federal government, as treasonous, violent disregard for a powerful centralized federal government is quite literally the premiere founding principle baked into the US's history.
Congress has zero power whatsoever whenever they lack the consent of the goverened. The functional legitimacy of the entire federal government is near zero - we're living in the orwellian nightmare where the military industrial complex more or less runs the entire show from behind the scenes - something Eisenhower tried to warn us about over half a century ago.