I think if you provide a service that basically creates a free public sphere, and you don't charge for it, it makes sense to consider what you're offering a public sphere and that just mean it has to be treated like one, where you should be free to speak up and mobilize peacefully.
If social platforms charge a fee, or subscription, then it is a private sphere, and I think platforms should be allowed to do whatever they want in that case.
Finally, the constitution only applies to lawful citizens of the US, which means that in order for platforms that would provide a free sphere of discourse, to be excluded from their enforcements, you would need to have performed full know your customers, and proven to the platform you are a real citizen of the US, with regularly having to re-proove that your account is still owned and used only by real citizen of the US. If you didn't provide this info and proved your status, the platform should be allowed to apply enforcement, because you could very well be a bot, or a foreigner.
Lastly, you should also have to speak non-anonymously, if you don't reveal your true identity to others in the public sphere, enforcement would still apply to you, because in a real-life public sphere people are not anonymous either, you should be able to know who is speaking.
Lastly, you shouldn't be allowed to make it look like you are more than one person, so use of multiple accounts and various pseudonyms if found should also make you eligible for enforcement again.
I think with these, it's reasonable on both front, prove you're a real US citizen, have a single public account that's not hiding your identity, go ahead and say what you want unrestricted, you're right to free speech applies. Otherwise, it's not clear you're someone who has a right to free speech, and therefore enforcement should be taking place.