Facebook removes all her groups. Cloudflare shuts down her websites. Youtube removes her videos. Google only leaves anti-Elizabeth Warren search results up, etc. Basically a major presidential candidate is completely locked out of having any pretense on the Internet whatsoever.
How many people who hold the above position, would say "yeah, this is fine. These are just private companies choosing who they want to associate with. Free speech doesn't apply here."
Congress shall make no law...
Although I suppose you could argue that once you have a handful of congressmen in your pocket, the First should apply to you too?
To answer your question more specifically: if Facebook is like a TV-channel, then they should be regulated like one: channels can broadcast what they want. If facebook is more like the TV medium then it's a different story. Then you can't have it arbitrarily cut access to certain interests. BUT in that case it's also probably "too big to have that responsibility in private hands" and something should perhaps be done about that (just like some banks may be "too big to fail" and as such can't be responsible for the economic damage they cause).
That implies having feasible alternatives when there are none.
Also, it implies you are aware information being prefiltered for you. Even if Warren knew about it and talked about it, she would sound like a conspiracy nut.
No alternatives to Google or Twitter? What?
Just because you don't like the venue or the service in no way makes them "infeasible". Just because you can't as effectively promote your cause doesn't make them "infeasible". There are other search engines besides Google, and there are other social media platforms besides Twitter, Facebook, and Reddit.
Any suggestion that a private company should be forced to broadcast speech that it finds distasteful is a direct affront to the 1st amendment, full stop.
8chan being denied access to another company's resources is in no way a free speech issue. In reality, 8chan's ideas are losing in the "marketplace of ideas" and now we have people who suggest government intervention to give their points of view a leg up.