in the UK we would say:...

who's this "we", white man?

OK maverick, I realise that I answered with too little thought and too glibly . I took the simple approach of looking at the examples given and no deeper. I agree with all your illustrations and am left only with the obvious conclusion that there is a difference in usage between the UK and the USA and maybe half a dozen other countries. Bridget's thoughts, with which I also agree, suggest that there are complex common usages that people are familiar with, but it is not clear, to me at least, (I am trying to be really cautious now ), that grammatical rules cover all these ramifications.

dxb