The First Amendment says this. Freedom of speech is “a principle that supports the freedom of an individual or a community to articulate their opinions and ideas without fear of retaliation, censorship, or legal sanction” [1]. It is broader than the First Amendment, and gave rise to it, though the First Amendment is its most successful codification in the modern world.
A society that shuns those who say “bad” things, even without state action, may not hold true to the values of freedom of speech.
You don't get to choose peoples reaction or the way they view you after you say something. That would be infringing on their right to hold or express opinions about your views.
What's complicated about that?
You say "[we] don't get to choose [people's reactions]", but this is not at all relevant. We're not asking whether their actions are legal or whether we can legally dictate what they think, we're asking whether they're acting ethically.
One is law, the other is a principle.
Freedom of speech means the government won't/can't prosecute you for what you say. It doesn't have anything to do with how companies or private citizens respond to your words.
You're (usually) legally allowed to say you'll fuck my mom but I don't have to bring you over for family dinner.
One could contend that apple's refusal to host this app on it's store is in itself free speech.
Either way, the government jasent gotten involved so nothing here treads on free speech issues.