There are well-established exceptions that include incitement to violence. Wikipedia's summary:

"Categories of speech that are given lesser or no protection by the First Amendment include obscenity (as determined by the Miller test), fraud, child pornography, speech integral to illegal conduct, speech that incites imminent lawless action, and regulation of commercial speech such as advertising."

https://en.wikipedia.org/wiki/Freedom_of_speech_in_the_Unite...

I cannot find any reference to that in the US constitution text.

So?

These exceptions are given. What’s your point?