It was the washington state supreme court. Though I freely admit I may be misinterpreting what they have to say, I’m far from a legal expert.
Here’s a couple of SCOTUS cases I found in my reading, both of these involved cross burning rather than actual words, but they seem to relate.
A more recent decision by the US supreme court is quite interesting, take a look at RAV v city of saint paul, decided in 1992. The city of St. Paul had an ordinance that prohibited fighting words that were based on ‘race, color, creed, religion or gender’. That ordinance was determined to be unconstitutional.
Virginia v Black (2002) is another interesting one. From a quick reading of it, they say that intent to indimidate is the primary factor. (prior rulings against the cross burner were overturned)
Overall from my reading it seems that this is far from a settled issue in legal terms. I haven’t found any cases yet that relate to someone using ‘fighting words’ and then being physically assaulted. So, how these two things would work in a practical sense, I don’t know.
Do you have any reference to a case that more relates to what the conversation was about? That is, is there a legal right/defense to physically assault someone over something they say to you? I would be interested in reading it.
I would just say though, even if there is a legal defense I still believe it is wrong. My personal feeling is that both the person that uses a slur and the person that physically assaults them are in the wrong, but I believe that using violence is more wrong.