I first noticed the general liberal shift toward this new 'standard' during the Obama administration years when Barack made it quite obvious that he loathed Israel and Israelis -- although looking back on it I now suspect that this was more likely than not to be outright Jew hatred from their holy and sacred Anointed One -- and workaday liberals began shifting their spoken foreign policy support to Palestinians instead in support of Barack.
I think that in the beginning it was just a new and thrilling fad for the average liberal -- this was before the term 'leftist' was generally being nosed about. But since those years it seems obvious that the 'fad' has gradually turned to full bore hatred; and so here we are today.