Restrictions on free speech only apply to the Federal Government. A Federal officer would never be able to get an injunction preventing you from speaking or writing something about a federal official, office, or person.
Otherwise, you have right to say or write anything you want about anything. If you say or write things that are derogatory, libelous,slander or untrue you can get sued. Period.
However, an opinion about something almost never gets involved in a law suit. News reporters, et al, do it all the time. Even when they call the President a dolt they can't be sued because an opinion is just that. It has no real substance. Listen close and you will hear how closely the talking heads parse their words to keep them opinion with no facts or actual slander or libel to argue against.
