No, this really isn't a First Amendment issue. You're free to say (post) anything you want just remember that anything that you say (post) can will be used against you.
The best example that I can come up with is in discussion about home invasions or burglaries (which are not the same thing) a given poster states that if he finds an intruder in his home he's going to kill them. He's going to go out of his way to make certain that they're dead or the people that post that you're always better off if there's only one story being told, IOW the bad guy is dead he can't tell his side of things.
God help you if you post things like that online and somebody ever breaks into your house and ends up dead. Because those posts will be read to the jury.
Massad Ayoob has written articles on this previously. One of the things that he said is one of the first things they'll do is subpoena all your Internet passwords and if you lie they will charge you with perjury.
They will find everything you've ever posted online and if they can use it against you they will