So did Americans until Eisenhower had pictures taken of the concentration camps. A Nazi rally of 20,000 took place in Madison square garden in 1939. Antisemitism was the norm in the US prior to WW2. The historic opinion of Jews should not be ones only defining line in the sand.
Seems like that was more just the last 2 months, the rhetoric conflating Jews with a few banking families seems to have been on the rise among "progressives" for a while now.
Have you seen this in person or just online? There's probably more bad actors trying to push antisemitism ideas onto the left then there are real people in those spaces. Eventually, real people get tired of arguing with bots and paid shills and just leave the online space, leaving only the idiots.
The problem with using hippie's as an example is that they aren't a monolith and many hippie groups were just some flavor of cult with no real political ideology at the top other then being anti-establishment. It's not surprising that many of them intermingle with neo-nazis, but hippies being left leaning is more a piece of fiction then history truth.
in person. "Hippie" is just my general term for ravers, burners, arty types, heavy drug users, marxists, and the types pushing polyamory as superior. I've been a few of these one time or another. Other than myself, and a few notable hard partiers from Texas and Saskatchewan, i've found right leaning hippies to be very rare.
In your case, just start reading, something, anything. Your education is severely lacking if you are seriously asking for references on Stalin's view of Jews.