If I belonged to a low status group that most people had no moral issues with abusing, then I would keep saying they behave immorally according to my views, and they would keep ignoring my words and abusing me. I fail to see what about this situation suggests that I behave as if I believe in realist morals.
And you would really be ok with them living by their morals and abusing you?
Of course I would not be OK. I would want them to change their behavior and I would try to change it. This would be because of my preferences as to how people should behave towards me. These preferences don't exist independently of me. Morals are a special kind of preferences.
Saying "there exist someone's morals but there do not exist morals by themselves" is exactly the same as saying "there exist someone's preferences but there do not exist preferences by themselves".
Here's the new thread for posting quotes, with the usual rules: