The point about Australian English is irrelevant. Australian English is correct in Australia and incorrect in America, just as American spellings are incorrect in Britain. Language is culture-specific.
Again, if you have no interest in the idea that some things are correct and others are incorrect, this will not appeal to you. But that is a postmodern relativistic position and not one that everyone agrees with.
Even if none of that is appealing to you, the simple fact that is the overwhelming majority of the US agrees that a certain dialect is “proper” English. It’s unclear to me why a small percentage of the population would be justified in having their dialect be on equal terms with the society-wide one. This really has nothing to do with race inherently and the same situation applies to say, Appalachian dialects.