The word “Master Race” is clearly equivalent to terms which were used by Nazis and so are today’s far right wing and alt-rights.
There are other communities which created similar narratives, especially from the 4chan side, and I think the origin of “PC Master Race” comes from there.
Someone didn’t think this through. Banning Master/slave oppresses the BDSM community. Well, it oppresses the Masters, at least. The slaves like a bit of oppression. It’s their raison d’être.
Joking aside, language is what the speaker means and nothing else. You can say something to ten people and they’ll all have their own interpretations. And they can all be wrong.
A classic a while back was some folk in Australia saying Captain Cook didn’t discover Australia because indigenous people had been there for thousands of years. That isn’t what discover means but it didn’t stop many being offended.
I’ve discovered lots of things in my lifetime. It doesn’t mean I was the first.