(vs. it's actual meaning as a guard against government suppression of speech)False, False, False! This is not how it works in US jurisprudence. Freedom of speech has to do with fundamental human rights and society. Government, being an important part of this, therefore must abide by Free Speech. However, private parties are also subject to it as well. Free Speech is fundamental, and even supersedes other rights, like property rights.
https://en.wikipedia.org/wiki/Marsh_v._Alabama
You can still shout whatever you want in the town square,
This is such a dishonest conceit. It's like some dictatorship declaring they have freedom of speech, because while they control the radio, TV, and newspapers, the opposition can still post pamphlets. No, I'm sorry, but the scales of relative power just don't work in a practical sense, either in my examples, or in the one you just proposed!
In 2019, it's like a farmer trying to assert property rights against airplanes overhead. Sorry, but laws do have to change in response to new technological realities.
but you aren't entitled to the audience of any particular publisher.
This is a conceit. The audience relationship is not with people and YouTube. It's with people and a particular creator. It's not the publisher refusing access to its audience. It's the publisher throwing up barriers to the audience.
If there were a monopoly on printing presses, the printing press company wouldn't be allowed to say, "It's my audience, you have no right to it. No Pro Democrat words get printed!" There was a monopoly on telephone wires. It's not as if they would have been allowed to say, "The people connected to my network are my audience! You are not entitled! No Democrat communications over my network!"
What you're defending is just a technological end-run around freedom of speech, which you support because it's your side that would hold all the power.