Yelling FIRE in theatre might be permitted under the 1st amendment, however, the supreme court did subsequently say that "These later decisions have fashioned the principle that the constitutional guarantees of free speech and free press do not permit a State to forbid or proscribe advocacy of the use of force or of law violation except where such advocacy is directed to inciting or producing imminent lawless action and is likely to incite or produce such action.[14]"
In other words, Trump's tweets and January 6th's speech can clearly be restricted on the grounds that they incite imminent lawless action.