Free speech doesn't require a platform to work nor any intermediary. It is a boundless idea.
Nowhere in my comment did I claim free speech requires a platform or an intermediary, they happen to be relevant in the context of the discussion we're having, just as television would be relevant to a discussion of free speech in broadcasting. Free speech doesn't require telecommunications infrastructure, yet it still applies, and broadcasters (even of public access stations) have the right to refuse to air content they don't want to.
You're the one putting limits on free speech despite also calling it a boundless idea.