He's also Jewish -- a fact which might surprise external observers familiar with how Momentum in general and Corbyn and particular have ridden a wave of antisemitic sentiment.
You might not believe me, but I really am not too familiar with Jon Lansman. I don't know if he's a good guy in a bad situation, or a crass as-a-Jew opportunist. For the purpose of this post, I don't need to know.
What I do know, and what this Nick Cohen column very effectively establishes, is that despite his unimpeachable credentials as a leftist and as a Corbynite, Jon Lansman would not be able to effectively combat antisemitism in his movement even if he tried. Why? Because the moment he does, he'll lose his credentials as a leftist and a Corbynite.
When Corbyn supporters cite the support of Lansman or groups such as the tiny Jewish Voices for Labour as evidence that accusations of left anti-Semitism are groundless, they argue in bad faith. If Lansman or any other Jew were to say they had gone too far and must change their behaviour, the left would denounce them.
When he challenged Corbyn’s appointee for the post of Labour general secretary, Corbyn supporters immediately told Lansman his views were worthless because he was ‘a Zionist infiltrator’, who puts ‘Israel above the left or even Britain’. In Leninist terms, the function of Jews on the modern left is to be useful idiots who can be dispensed with as soon as their usefulness ends.There's a mythology out there that people don't listen to antisemitism claims because Jews "cry antisemitism" all the time. The corollary to that is that, were there Jews who were better Jews -- Good Jews -- and didn't engage in such abominable behavior, then their call-outs of antisemitism would get attention and a fair hearing.
And I suspect at least some Jews (I have no idea if Lansman is one of them) really believe this. They think "I'm not -- I've shown I'm not -- one of those Jews. I acknowledge that antisemitism claims are sometimes (often, usually) a bad faith smear. I've proven myself a good comrade. I've earned my credits. So if I say somethings antisemitic, I can cash those chips."
It doesn't work. It never works. The minute you go to that well, you'll find out it's dry. Even a group like JVP -- whom you'd think could never be accused of being too quick on the antisemitism trigger -- still falls victim to it on the rare occasions they do try to levy a claim of antisemitism against one of their "friends".
Because they're not actually thought of as epistemically reliable. They're not trusted independent of their utility in propping up the previously-arrived-at conclusions of their putative allies. And once they stop serving that function, the antisemitic default rises back up -- a Jew who disagrees with you is a Jew who's probably lying, probably part of the conspiracy, probably [hiss] a Zionist. It doesn't matter what your credentials are. The threshold bar for talking too much about antisemitism is talking about antisemitism, period.
In a sense, this makes me more sympathetic to Lansman than you might expect. He's in a trap he can't escape from; there's no way for him to be an influential leftist and a prominent critic of antisemitism in his movement at the same time. There's no trick -- neither ironclad arguments nor impeccable left credentials -- that would force people to let him occupy both worlds. He is in what Memmi calls an "impossible condition", one "which can have no solution in its actual structure." Without being too glib about it, when you think the reason people gaslight, deride, and dismiss Jewish testimony is because of the Jews, and not the antisemitism, of course you'll fail to see the trap. But in an antisemitic society, Jews get no usable credits for being Good.