It seems like wherever he turned there was a black authority figure checking him.

By the time he went to HR, he probably thought he was in a Kafka novel.

“Does this mean we can finally say the word n-----?”

The word 'finally' moved it from simply doing his job to a very off color joke.

But they were very extra with it. Especially the HR person with her "Why are still using that word" business.
You asked him to tell you what happened, and he told you.

I think he has a good case. NOBODY should be using that word all loosy goosy.
If the white guy gets punished, then everybody who uses it should be punished