Should Twitter and Facebook be Regulated as Utilities?

The Constitution guarantees every citizen the right of free speech. But what happens when the most effective channels for that speech are corporations such as Twitter and Facebook? Does the government have an obligation to make sure those companies are not limiting free speech for some classes of users?

My sketchy understanding of the law is that the government is only responsible for making sure the government itself is not abridging free speech. I think most of us agree that we don’t want the government volunteering for any more work than the constitution says it should be doing.

But shouldn’t the federal government get involved if a few monopoly corporations start to control the national conversation by filtering out voices that disagree with them? 

That seems to be the situation right now. For example, Twitter is apparently “shadowbanning” me because of my past Trump tweets, or so I assume. That means my tweets only go out to a subset of my followers. The rest don’t know I tweeted. My followers tell me this is the case. They have to visit my timeline to see my tweets.

@ScottAdamsSays Your tweets are not at all showing up in my tweetfeed.