Another layer of the left antisemitism is, as the "left" would call it, colonial mindset. Owen Jones is the best example of that, at the beginning of the Russian full scale invasion on Ukraine he, without any hesitation, posted on twitter that Russia has a right to do that because Ukraine was always theirs sphere of interest. Thus, Ukrainians are not subjects but objects of politics and history - that is, imho, a classical definition of colonialism. And Russia is the biggest colonial power that ever existed. British Empire does not have as many killed languages, cultures and nations on its record as Russia throughout the centuries. These people have the superiority complex and they think about world in these realms. That is why they understand Russia, the only twist in this mindset is negative- exceptionalims - only USA/UK/"The West" can do wrong. But when it comes to thinking about people and nations that were objectified by Russia they can only see through the colonial lenses. I would say "The left" is not able to see more than the other to Russian greatness. Russia has culture, language and in general everything is great. The West is not great anymore because it did bad things. However, Russia is different because of history. As Russia was the enemy during Cold War, and of course it was an enemy because of communism, there was nothing else, it must be the good one. All nations that Russia colonised are just inferior - Easter Europe* - no distinctive cultures, no distinctive languages with their quirks etc. just amalgamate of some stupid people. Eastern Europe is not even defined geographically, there is only one factor that is common for all countries that ever been counted as Eastern European - is the fact of being victim of Russian imperialism.
The biggest enemy of our exceptionally great but bad "West" must be right, because it is a match of equals. Communist Russia was great at playing the saviour of the world, but why people are so ignorant about history is beyond me.
A man who described genocide and made it a crime, Rafal Lemkin was a Polish Jew, born when Poland was still under rule of three imperialistic powers and, to say it frankly, Jews in parts of Poland that were incorporated by Russia had it really bad. Pogroms, ghettos, and all the pleasantries. However, ethnic Poles were also repressed*. In his original proposition, that was rejected at the UN Conference under Soviet influence, it was very clear that historical experiences of Polish nationals were important in his process. Russia just cannot let the world learn that. history of Poland or Ukraine is much closer to the case of Israel than Irish experiences. Russia strategically has to be a champion of the underdog (in this case Arabs, doesn't matter which country and at what cost).
Ukraine, as an independent country is younger than most countries 'the left' would chose to point on the map when asked about the British colonialism. Pakistan - older, Zimbabwe - 11 years of independence more etc. Poland was eradicated of the map of Europe for longer than 100 years. Similarly to Jewish Diaspora the language and culture survived without the country only by the power of community and its determination. Try to tell Poles that they should apologise to Germans, Austrians and Russians for not accepting that they decided it is their land now and Poland should never try for independence - well, some Germans believe that half of modern Poland should be German, but that's another issue.
I have a friend who is a Silesian, now region of Poland, but for many years it was German territory. The history is complicated, but she said many times she has no doubts about Israel's right of existence. It is easy to say that some nations should never have their own states, on their own land when you were never colonised. This experience of non- experience is shared by "the left" of the west and Russians.
Long story short: The western left is not as anti colonial as they like to think. Sorry for the rumbling, it is late and I am bit emotional on the subject, but I hope in the end it is readable.
*Soviets were never marxists, they had their own version written by Lenin, and the system was nowhere near communism as described by Marx.
**funny thing, Herzl, the guy who invented the evil zionism was not that keen on "Eastern European" Jews as well, exactly because of this historical narrative plus, as it is usually with colonised countries, Jews from "Eastern Europe" were absolutely poor and used to not exactly ideal living conditions.
* Wikipedia states that Lemkin was solely motivated by his experience of Holocaust, that is not true. He started theoretical work on definition before the IIWW. He was shocked when learnt about Massacre of Armenians by Turkish forces. I think, and yes of course I am unhinged blahblabhla, it is another case of narrative antisemitism. A Jewish man could not possibly do something for the benefit of humanity, Jews always think about themselves.