It means you have the absolute right to say anything you want to say. It also means you can say something without being a hypocrite, as you are free to speak on a particluar topic you have knowledge on or have not committed whatever you are condemning.
Many people misunderstand the term freedom of speech with regards US federal law. That law is a specific protection from the federal government for citizens, businesses, and other organizations. It is specifically to protect them from retaliation by the federal government.
It is important to note that the law does not protect citizens, businesses, or organiztions from each other. Such protections would be from local laws regarding defamation or libel.