And on the flipside, these companies have grown to the point they could be considered a public utility or even monopoly. There certainly is precedent for governments compelling utility providers to not restrict their services arbitrarily.
You are playing word salad with lots of different concepts and it looks like you are making hypotheticals with what we could make companies do.
Companies growing does not make them into utilities. Utilities are providers of very specific commodity services which are specifically defined by statutory law.
Monopolies (as in anti-trust law) are companies which abuse their power to hurt the consumer. Traditional anti-trust law doesn't work against social media companies because consumers pay no cash for the transactions. We could change anti-trust law, but since there is no analog, it's not clear what we would change it to.
> There certainly is precedent for governments compelling utility providers to not restrict their services arbitrarily.
There is also precedent for governments to uphold a concept of "decency" (the same government that defines it as "I know it when I see it") which communities can judge for themselves, without a written definition. I, personally, don't see the judgements that social media companies make as "arbitrary" (they do have written ToS and they attempt to give their content moderators guidelines/baselines for judging decisions).
> the idea of Twitter and other social networks being utilities isn't something I invented
Fair enough. I don't blame you. I just don't think it's easy or reasonable to overload the word "utility" as applied to content, which is exactly why it's currently governed by Section 230 and not Common Carrier.