Historical racism is largely interpreted today as hate directed towards minority groups. Very roughly: people were racist because they hated X or Y, that was some defect in their personality, some individual reason, mental illness, etc.

But it was also a function of group dynamics and attempting to preserve cohesion (perhaps more commonly, I think actively hating people you don't know has always been regarded as odd). Outsiders were discriminated against in order to maintain the values of the group (ignoring for a second whether these values were good or bad).

And this kind of collective thinking is something that is more typical of the left. So you are seeing more and more of this reverse discrimination. And will continue to do so because this instinct towards group cohesion is overwhelming.

You also see this outside the US with left-wing nationalist groups. I think there a tacit assumption today that left-wing and nationalism cannot go together. But nationalism has often been a key source of group cohesion for left-wing movements, and that has (unfortunately) often been defined exclusively.

To say this another way: this has to end up with more discrimination. Everything that you do as an adult today is set against your record of "privilege". Why do people pretend to be poor? Why do people pretend to be a different race? And the people doing this are apparently privileged ones? It makes no sense.