I think before you could argue he was simply rubbing shoulders with bad people as an unfortunate consequence of being a Palestinian rights campaigner. And you could say that the Labour party has handled the Anti-Semitism issue poorly.
Now though, with this, I don't really see how you can any longer claim that he's not personally anti Semitic. He's not a BNP style, "kike yid" racist, but this is classic "othering". Even if you give him an enormous level of benefit of doubt that, frankly, he's long since burned through, and assume he is talking about very specific people, rather than Jews or even Zionists generally, this is still abti-semitic. He's specifically saying that "you being, despite being here all your loves, aren't sufficiently English." It doesn't matter if he's talking about a specific person or specific set of people - that's utterly racist to suggest that because of a political difference, they aren't as English as him (and apparantly don't understand "English irony" as well as the Palestinian envoy?)
But of course, he wasn't talking about specific people. Obviously he wasn't. Obviously he wasn't talking about a mixed group who included both Jewish and non-Jewish people. It doesn't make sense. To use an example I've seen floating around on Twitter, Tony Blair is a zionist. He's lived in the UK most of his life. Even if he had been at the parliamentary event (staying thankfully silent during it, natch) and then came up to contest the contents after - would *any* of what Corbyn said make sense? Not even remotely. He was talking about Jews, plain and simple. And he thinks that, because they disagree with him, aren't really English. And if they're not really English, what are they? They must have some sort of loyalty to something else.