Fighting words is a thing, but it is protections for person in court. They can prove the other person was the aggressor due to his words, kinda saying he was the first person to throw a punch, even though it was speech. Not something a cop can arrest you for.
Like:
Person A: All niggars must hang!
Person B punches person A.
Person B's charges are dropped due to the fighting words clause.
This is a state by state thing, not all have it.