Imagine an American progressive telling an enrolled Native American that because they had majority European ancestry and looked white, they weren't actually a member of their tribe ethnically, never could be, and couldn't have any connection to their tribe's ancestral homelands.
Not even a believable hypothetical, right? 100% violative of progressive views about identity.
And yet progressives in large numbers have no hesitation to doing exactly that to Jews.
What else could we call singling out Jews to be subject to a double standard except anti-semitism.
But, ironically, progressives will deny their anti-semitism by doubling down: you can't be anti-semitic towards people who aren't actually Jews.
But imagine trying that same line with respect to Native Americans.