Exceptions to freedom of speech in America (these are off the top of my head, so I may be missing some):
- You cannot yell "Fire!" in a crowded theater unless there is a fire.
- No speech that presents a "clear and present danger".
- No false advertising.
- You cannot divulge classified information.
- You cannot commit perjury.
- Defamation, libel, and slander are not protected.
- Obscene material has limited protection. Child pornography has no protection.
- The government may make reasonable restrictions on time, place, and manner of speech.
Other than that, you may say anything that is enlightening, inspiring, noble, intelligent, humble, truthful, stupid, worthless, hateful, bigoted, arrogant, offensive, etc.