Freedom of speech is tough, huh? And in the USA it doesn't protect against promoting threats of violence. Seeing as the N word is probably considered the most hateful word in the English language, I can see it being understandably considered violent in many cases.
It is absolutely not literally violence to say or call someone the N word, no matter how repugnant or socially unacceptable it is. It is not illegal in the US to call people horrible names, nor is it illegal to be racist, homophobic, transphobic, etc.
This isn’t to say I advocate for people being any of those things, it’s just somehow become generally accepted that these things are somehow inherently breaking the law or some kind of hate crime. Even on the rare instance someone displays some racist material in public, the news is quick to say police are investigating…investigating what, exactly? “Hate speech” is not a crime in the US.