Well, for those who still stand on the Constitution, it states "Congress shall make no law.... abridging the freedom of speech or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances." It is funny that those who don't believe in absolute freedom of speech do stand for absolute freedom of the [leftist-liberal] press.
number of ideological challenges have arisen in recent years to overturn this norm
We don't have a clause in the constitution stating that it can be overturned by an ideological challenge. It requires and amendment ratified by three fourths of the several States. Ideological overthrow is resorted to by leftists, Clinton and Soros because they cannot muster 3/4ths of the states to consent to an amendment, even if you could get a very venal craven corrupt Congress to agree to it, though I would suggest that 1/3 of the Senate would in any case oppose it.
But there you have it, leftists trying to suggest that something is subject to debate when it isn't open for debate at all, until you get the proposal to the states.
Liberals say they and they alone are love, rational, educated, smart, good.
This makes everyone else by definition a stupid, crazy, evil hater.
By their own definition, hate speech is every other viewpoint.
When we allowed for free speech to be curtailed when it is called hate speech, akin to inciting a riot, we gave them the means to shut down every other opinion per their own branding.