Just so we’re on the same page, “fire in a crowded theater” was coined as part of the Supreme Court’s upholding of a conviction for protesting the draft during WW1. The decision is no longer really relevant, having been replaced in a later case with a revised test that requires that the speech in question is intended to, and likely to cause, imminent lawless action. Which is for the best, because the Schenck decision hails from an era of the Supreme Court that was decidedly less tolerant of individual speech.

None of that is relevant here, because defamation is an established exception to the 1st amendment, totally separate from incitement of lawless action.