Believe it or not, I don't like impugning people's good faith, and only do so as a last resort when I'm wondering if I'm wasting my time arguing with someone who's just interested in getting a rise out of people rather than exchanging honest opinions. These types, we'll agree, are sadly all too common on the internet. Anyway, the fact that you are going to such lengths to answer this contention (something I hadn't seen you do before) convinces me that you are sincere.
I maintain that you
are applying a double standard, though, even if you're doing so sincerely. The fact that you admit that your "complex calculation" largely boils down to "gut feeling" should be a pretty obvious clue that you might be letting your partisan views color your reaction to various instances of antisemitism based on who they originate from. This takes at least two forms I've noticed. The first is that, while you claim to have lost your naivety about right-wing antisemitism (and yes, it still remains absolutely baffling and frankly inexcusable that you ever harbored such naivety considering not only the Shoah but
the long and rich history of postwar neofascist/neonazi movements of which modern European far-right parties are often direct successors), I haven't really seen you act on it. You claim to be conflicted about Fidesz and other such movements, but every time that a discussion on them appears on Atlas, you act like a fanboy, not like someone who appreciates their political project but is deeply troubled by some aspects of their rhetoric.
Obviously, the most important double standard is your assessment itself. Now,
my thoughts on anti-Zionism are well documented on this forum, so let's please avoid strawmen. If an actual, overt anti-Zionist was the leader of a left-wing party in a country with significant foreign policy clout, then yes, I would agree that that leader would pose a bigger threat to Jews worldwide than Orban. However, this has never been the issue with Corbyn. All you can accuse Corbyn of is 1. to associate with such people for the sake of political convenience, 2. to be deeply insensitive toward people who are rightly offended by that, and 3. to himself have specific circumstanced stances against the current Israeli government's behavior. Now, 1 and 2 are certainly bad things, and again, I'm on the record here condemning them in unambiguous terms. But none poses the kind of existential threat to Israel that you're talking about here - the people Corbyn associated with don't have any serious influence on his foreign policy, and he
has, if half-heartedly and belatedly, distanced himself from them. There is so indication so far that Corbyn questions Israel's right to exist.
Now, if you want to say questioning specific actions by the current Israeli government is inherently antisemitic, I hope you realize the consequences of what you're saying. You're saying that, by virtue of a State providing a safe haven for an ethnic minority, any action by whoever happens to hold the reins of power in that State is beyond criticism. Surely you realize what an absurd principle it is. Now, a lot of criticisms of Israel's actions do use rhetoric that's based on antisemitic tropes or is otherwise insensitive to Jewish culture and history - that was the core of the issue with Omar's comments. I actually don't know if Corbyn himself has done so, but let's assume for the sake of argument that he has. Do those comments, in and of themselves, pose a greater threat to Jews worldwide than the kind of antisemitic dog-whistling that Orban&friends use? Now, I might be wrong about this, but my impression is that antisemitic acts are generally far more prevalent in Eastern European countries with Orban-like politicians either in power or otherwise as heads of powerful parties, than they are in the UK or in Minnesota.
And do criticisms of the Israeli government's actions, even unfair ones, threaten its continued existence?
How? At most, they could lead to a country providing less aid and support to Israel, which, yes, would be an unfortunate outcome, but still a far cry from threatening its survival, unless you want to go all in on a slippery slope fallacy. No serious leader of a western country would ever consider letting Israel be obliterated, let alone actively militate for that. Corbyn has certainly given no indication that he would do either (Omar seems potentially liable to do the former, but luckily she'll never be in a position to). You might disagree with the two-state solution, but its implementation would,
by definition, imply Israel's continued existence, so the whole "insurance policy" argument falls flat here.