For example, this Tuesday in the pub after our local Stop the War Coalition meeting there was a discussion about the US presidential elections, and one well respected socialist activist expressed the opinion that Israel decided who the US president would be, and a member of the Green Party agreed that Jews still controlled most of the world’s money. Of course other people, including myself, challenged these views.
The individuals concerned would be horrified to be called anti-Semitic. Indeed I am sure they are not prejudiced at all against individual Jews, but they have bought into anti-Semitic narratives. The worrying thing is that so much of the left seems to ignore this problem.
That was at least challenged. Not long ago Duncan Money wrote:
Anti-Semitism does exist on the left and for any anti-fascist this is disturbing. The first demo I ever went on, a couple of years back, was a pretty boring counter-demonstration against the National Front and one of the first things I noticed was that on the march was a middle-aged woman carrying a placard reading 'Israel stop controlling Britain and America!' accompanied with a swastika and an Israeli flag. Here we were marching against fascists and no-one challenged her.
On top of that, there were stories of "peace" protests in France and Britain with groups breaking off to beat up Jews. The infamous posters below from anti-war rallies (documented by zombietime)
And, of course, historical examples abound. Nazi control of Germany did not develop from a far-right movement becoming mainstream. It was far more complicated than that and involved people on the left (or who moved from the left) who were committed to the Nazis. In the Boer War, Left antisemitism was key to the anti-war movement. And let's not forget Stalin, whose antisemitic propaganda resounds today.
Call it a "new antisemitism," or the same old antisemitism. Call these people fascists successfully pretending to be on the left. Or call it antisemitism that pervades society from right to left. Make a point of saying that you still think right-wing antisemitism is more dangerous (even though I'd disagree with you on that for a few reasons). In any case, I don't care much about how you want to conceptualize that, so long as you acknowledge that antisemitism exists on the Left. It's prominent on the Left. And it's a problem.
At the march Duncan was talking about, an antifascist protest!, no one thought it was enough of a problem to confront that women who felt that Jews control the US and Britain. That, right there is classic antisemitism, and when antifascists are ignoring it, we have a problem.