Anyways, I sympathize - I think generating outrage on HN is about your best option. But let's not talk about illegality here, it's still a free service. You're not going to get free human time from any other kind of company, so why should internet companies give it to you?
also I didn't say don't ban. I said don't shadowban. that's worse than banning.
If a private entity de-platforms you, you will have no claim against them, unless you have a contract with them that's been violated (i.e. you pay for the services and they deny the said service). If I stuff a sock in your mouth and tape it up, I'd be liable for the assault & battery, not for the first amendment violation. If a government official stuffs a sock in your mouth and tape it up - you might have a chance to claim first amendment violation, but even then it might be a stretch :)
I could even see it as a potential way to balance public and private interests - if you try to consolidate too much - you run the risk of losing your private status and becomes a mix of private/public company, where some of the protections afforded to private businesses no longer apply.
There have been examples of these things happening, notably how railway became so dominant around the world that governments intervened and nationalised them. There's no way of knowing how long the current tech giant status quo will last - will it get worse or will they get slapped down.
But yeah shadowbanning really isn't nice and I agree that it shouldn't be used against actual humans who just wanted to say something. It's an important tool against bots and propagandists (I mean state-sponsored actors here) though.
oh and, it's important against bots on paper. I don't know if you use twitter but it's a mess with respect to bots...
I don't use Twitter but I run a small platform (oldschool forum) and without shadowbanning it'd be impossible to curb the bots. They immediately react to a classic ban.