The “fire in a crowded theater” is an oft cited example that highlights this point. The phrase is a paraphrasing of a dictum from an opinion in Schenck v. United States, which held that the defendant's speech in opposition to the draft during World War I was not protected by the First Amendment.

Holmes argued, "the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent."

It’s a great example of how governments abuse these powers to silence inconvenient speech.

From child pornography to robocalls, I’d suggest that you don’t need “speech” to be a crime - though it’d be convenient to many pro-censorship arguments if it were.

The production of pornography without consent is illegal and is not speech. The production and possession of child pornography is a crime. Transmission requires both, which are already crimes. Possession with intent to distribute and the distribution of this content are already crimes.

You don’t need a carve out for sending these over TCP/IP conflating it with speech any more than you need a carve out for sending the photos through the U.S. postal service. It was a crime before you sent the photos, still a crime after. Free speech doesn’t wash the crime away and you don’t need to ask us to give up free speech to charge them with a crime.