The "fire in a crowded theater" argument was created by advocates of the prevailing moral panic, in fact. The panic in question was anti-war and anti-draft propaganda by socialist parties in the USA during WW1, and the phrase originated in a Supreme Court ruling that said that it's legal for the federal government to imprison people for speaking such horrible things.

It never ceases to amaze me how common this trope remains in defense of censorship, given that it was designed as a slippery slope.

https://en.wikipedia.org/wiki/Schenck_v._United_States