FB, Twitter etc are essentially microphones. They give you a microphone to use with terms and conditions. They can choose to take that mic away if you don't follow their rules of use. They are not part of the govt.
Those companies decided to limit amplification of certain users who were in violation of those rules. The govt didn't mandate any action social media companies took. So long as the govt did not mandate their rules and enforcement, it isn't a violation of your constitutional rights. I think it was warranted by the threat to public safety to ask for a review.
The irony is that you being mislead into believing they somehow compromised your rights by asking companies to address 'fake news' proliferating on their platform has caused your discontent.
You should really do a better job evaluating your sources, because if this case is an indication, your sources are not very good.