The government notifying Facebook that someone posted content contrary to Facebook's TOS doesn't violate the rights of the person violating said TOS. You never had a right to post content that violates the TOS you agreed to in the first place.

You do have a right to share that same content on your own website and the government would have no right to make you take it down.

In no cases were people unable to express their opinions. They were unable to create posts or comments contrary to the terms of service of the site they were using to share said opinions. Much like neither of US may herein violate the terms of Hacker News.