Well, the lack of apology was given particular emphasis on the piece.
But, more problematically, I don’t see how the exchange you cite demonstrates your central thesis: that white people lump all non-white people into the same category. Because that certainly would be racist, if true.
I can only speak for myself when I say that I don’t think it’s true. I also don’t think it’s likely to be true among most Sanders/Warren/Buttigieg supporters. But I don’t know. I haven’t polled them.
Most importantly, I don’t know how to respond to an essay like this without making things worse. I’m not going to plead guilty to something I’m not guilty of — I don’t think anyone should.