So how do you propose forums deal with spam?
Seriously.
That is the price for avoiding liability: To be able to say you had nothing to do with it beyond providing a platform and abiding other applicable laws.
Prepare for a world of spam like: "Your car's extended warranty is about to expire unless you act NOW. Press 1 to connect to a specialist, or press 2 to acknowledge that the FCC should be dismantled."
All of a sudden, removing spam is stifling political speech and is forbidden.
First you agree on the principles, and then you can talk about how they might be implemented and regulated. Do you agree in general that political opinion should not be punished or censored? If not you can just say that, no need to come up with increasingly byzantine ways that it couldn't be made to work.
In principal, I think the 1st amendment protects us from the government censoring speech, not from private parties doing so.
They are. The problem is such people want that freedom with none of the liability.
And it's not depending on us sharing those axioms, the point was to establish what the fundamental stance is on the point being debated. Presumably we're commenting on American courts, American laws, affecting Americans and an American corporation, so it seems like a good thing we're using a rather American frame of reference.