The internet should be a public utility. I agree with that.

But social media? I don't know. I mean, maybe there is an argument that once a platform hits a certain number of users it could be considered, but where is that line? Like, if a new social media site popped up tomorrow, do you think that shouldn't be privately owned/controlled?

Even if you did come up some number, how can we know if those users are unique? Theoretically, if you said a social media platform couldn't be privately controlled once they reached a certain number of users, anyone could create a bunch of accounts to push the platform over that number. You could have a situation where half the accounts, maybe more, were only created to hit a goal. Would that make it necessary to remove private control?

And if we say it's not about the number of users, but rather how much influence the platform has, how do we judge that? Or should we even judge that? 15 years ago, Myspace was a pretty big deal, but now no one cares about it. Will Facebook or Twitter still be around in 10 years or will people move on to something else?

That said, I do get your point. Banning people from a large public discourse will cause them to seek out their own echo chambers which will only make them more extreme in their beliefs. In theory, hearing discourse from both sides should help to keep people in check so they don't become too extreme in their beliefs. However, even without banning people from these platforms, they tend to seek out echo chambers anyway. You really can't make people honestly listen to both sides or prevent people from becoming extreme in their beliefs.