Your comment has made me realize that I could have written my original comment more clearly; my dissatisfaction isn't about political agendas, but about deception – promoting free speech for the moment as a tactic rather than out of a dedication to the ideal, while claiming the latter.
Indeed, when people say "let's keep politics out of it", they're in effect trying to quell any challenge to the status quo, which arguably is inherently political, and this should probably be called out more often.
"You deplore the demonstrations taking place in Birmingham. But your statement, I am sorry to say, fails to express a similar concern for the conditions that brought about the demonstrations." From "Letter from a Birmingham Jail", which everyone should read: https://www.africa.upenn.edu/Articles_Gen/Letter_Birmingham....
This is a pretty uncharitable take, and one that I see too often.
I could just as easily say that people pressure others into turning every space political because they feel entitled to dominate every space with their politics, and they cannot tolerate any kind of truce or neutral ground. It's just another tactic to control the conversation.
And I think you're right! It seems very likely to me that that happens.
Playing devil's advocate for myself, however: the comment was not uncharitable because it did not attribute intent. Someone saying "let's keep politics out of it" may be trying to avoid conflict or simply be respectful, but unknowingly in effect quashing challenges to the status quo.
The comment was meant to be an observation of unwitting outcomes rather than secret intentions, but maybe that's in fact what you're objecting to ("it's easy to be pessimistic about the aggregate effects of small, inoccuous actions, and that attitude deserves some pushback").
Libertarianism works better without libertarians. It works better with collectivists than individualists. It works better with people who care about other people's freedoms than with those who care about their own freedoms.
Freedom of speech as a negative liberty means that the government does not criminalize speech. Some people would like to extend that to other powerful entities banning / limiting speech, but then the government would be suppressing those entities' other liberties.
The freedom of speech people care about is a positive liberty. It's about being entitled to have a platform for your speech. Maybe even a platform with an audience, or a platform you feel safe to use. In order for your opponents to have freedom of speech – a platform – your liberties must be suppressed. Either by an authority by force, or by yourself voluntarily.
Ultimately, freedom of speech is about you being obligated not to confiscate the megaphone.
What’s the paradox there?
If I attend a political rally and the speaker uses a megaphone, that's fine, I have consented to it's use.
However other places I have witnessed their use has questionable legality due to breach of the peace because the audience has not consented e.g. getting heckled when entering a University site or getting assailed by someone promoting their batshit Christian cult when trying to do some shopping. I don't think anyone would assume a universal right to make unwanted amplified noise.
Of course we disagree with our political opponents and feel that the policies they advocate are not optimal. It might be convenient to your politics if your opposition’s voice is dampened, but your opposition feels the same of your voice and does so for reasons no less sincere than your own.
That’s the fundamental bargain. You are neither obligated to hand anyone a megaphone, nor obligated to confiscate theirs.