No that's the 100% correct stance to take. You are not forced to use Apple's products or their walled garden, and they are not required to grant you access.
> I'm sure many oppressive regimes would be more than happy to permit that definition of "freedom of speech"
Can we drop the hyperbole and focus on the discussion please?
It doesn't matter if you're forced or not. In a world where the majority chooses to use them (for other reasons, e.g. convenience, features, price, etc), the company controlling what's broadcast on them is censorship, and has the same effects as censoring the publishing of a book had in 1700.
If the majority had chosen those platforms with the EXPLICIT goal of avoiding your content that would be another thing.
They're not granting me access, they're restricting my access to content they don't own. They have no real right to deny me access.
It's always better to concentrate at what we think SHOULD be the right or what it's we consider ethical, than merely restating what happens to be the law, which can very easily be BS.
And "whether we like it or not" plays a huge role in having laws changed -- that's where we should be starting from, not waving it away as if we're some kind of non-citizen slaves where things are just forced upon us.