I think most people's idea of free speech doesn't align with what you are saying.
Obviously you should be allowed to boot people from your house for being an asshole. And many businesses should probably also have the same right.
But there's also the ambiguities that mean it should be as simple as 'private property overrides everything else'. Some companies are utilities, and can't dictate whether someone can use their service based on personal views (electricity companies, water companies, telephone networks, etc). Sometimes someone's role means they can't be that selective about what they hear, like how a judge found it was unconstitutional for Trump to block people on Twitter. And there are issues about either public vs private property (like for company towns) or instances where a company is so large and has such a huge share of the market (like a monopoly) that you could argue whether they should be able to pick and choose what they like.
There is no real argument that a company like Reddit must adhere to free speech. No one forces you to use facebook, reddit, or any other website.
It does not mean "I can say what I want and you have to leave me do it".
There's plenty of material in the philosophical world about freedom of speech in regards to censorship by private parties and other people.