A few reasons:
1. The belief that Jews are white. This comes with two corollaries: 1. Anti-semitism against White Jews doesn’t matter because they’re white. 2. Racism against Jews of Color matters, but anti-semitism doesn’t.
Case in point, this article in the Daily Dot which totally ignores the fact that Magneto was a Holocaust survivor.
Regardless of their varying cinematic quality, the X-Men movies have always been good at building this political allegory without becoming overly preachy. However, they’ve also been downright abysmal at acknowledging people who face this type of discrimination in real life. The only exception is Charles Xavier, who as a character with a physical disability is near-unique as a blockbuster movie protagonist.
If the Holocaust isn’t discrimination in real life, I don’t know what is. But Magneto’s “whiteness” somehow cancels that out.
2. Media Apathy. Despite Jews being the targets of 60% of the “anti-religious” hate crimes in the USA, mainstream news sources don’t report on it. And when they do report on it, it rarely gets much attention. I had to actively look for information about Frazier Glenn Miller’s trial. Half the sites covering the #BoycottStarWarsEpisode7 tag didn’t mention the anti-semitism targeting J.J. Abrams. Discussion of the Charlie Hebdo shootings tend to focus on whether or not Charlie Hebdo was Islamophobic, but pays at best lip service to the Hyper Cacher murders which were connected and deliberately targeted Jews at a Kosher Grocery store. Meanwhile half of all racist hate crimes in France target Jews who make up less than 1% of the population.
3. Confirmation Bias. There are Israel critics who try to take in all the valid information and make fair statements, but they are nowhere near common enough. There are others who have decided that any Jewish voice that disagrees with them on anything must be an evil Zionist Hasbranik working for the Mossad to destroy their precious bodily fluids. Any article or information about Jews suffering is distrusted because it might lend any credence at all to the notion that Israel exists to combat anti-semitism. Accepting the narrative that anti-semitism still exists means that they can no longer be 100% certain that Zionism is wrong in all instances, which means that they need to fight to keep that precious certainty. Most people don’t seem to want to put in the effort to listen to voices they’re trying to tune out in order to keep their sense of moral clarity. This is a pretty good article on confirmation bias and why it’s a problem. The way that internet communication works makes it easier for people to only hear the information they want to hear, while filtering out the information they don’t. Since there is some overlap between anti-anti-semitism and pro-Israel activism, many people tune out all anti-anti-semitism activism for fear of having their beliefs challenged, even though one can fight anti-semitism and still be anti-Israel. This fear is often so strong that anti-Israel activists are often willing to listen to NAZIS and KKK leaders before they will listen to Jews. THINK ABOUT THAT FOR A SECOND.
4. Anti-Semitic Beliefs. Conscious or unconscious there are tons of anti-semitic ideas visible in the social justice movement. Many of them revolve around the ideas that Jews are all Rich and Jews control the Media. Those are stereotypes that aren’t true, but I’ve seen some people actually working backwards to make the case that, for example, Rupert Murdoch must be Jewish because he’s rich and is a major player in the media even though he is most definitely not Jewish. There is also a disproportionate focus on Jews who are rich and powerful and abusive like Sheldon Adelson while the Jewishness of anti-establishment figures like Naomi Klein is downplayed and ignored because she doesn’t play to stereotype. It’s also easier to tune out anti-semitism if you believe that Ashkenazim “aren’t real Jews” but Khazars which, even if that were true (which it most assuredly isn’t) wouldn’t rule out the fact that we were still murdered in the millions during the Holocaust for being Jews. But call anyone out on this and you’ll get a “anti-zionist not anti-semitic.” Again, they don’t want to risk having their confirmation bias exposed.
5. A Poor Understanding of Jewish Peoplehood as it Relates to Diaspora and Race. Tumblr social justice tends to be built on Critical Race Theory and Post-Colonial Theory. But in practice, one gets the feeling that most users really only engage in these concepts to the point where they understand two categories within each context: White/PoC and Colonizer/Indigenous. Jews, being a diasporic people for centuries, don’t neatly fit into either category. Most of us have lived in countries where we were not considered “indigenous” due to exile. As a result, over the millenia we have blended with many of the local populations resulting in genetically and culturally related groups that wouldn’t be considered the same “race” today. Critical Race Theory largely describes Racial politics within the United States. Post-Colonial Theory doesn’t do a very good job of dealing with diasporic populations whose indigineity has been rendered unspeakably complex due to residing as a frequently unwanted minority in other countries for centuries. What happens then is that Jews are frequently refugees, kicked out of various countries because the majority populations decided they didn’t want us. So where then do we have indigenous rights when the majority of us have been a refugee people for centuries? The denial of a safe home for Jews is an issue that many on the tumblr left simply don’t want to acknowledge or reckon with. So they act like Jews fleeing Nazism in the 1930s are no different than European colonialists who were looking for people and resources to exploit. They ignore the various persecutions against Jews in the Soviet Union because Communism is a popular meme. They ignore the expulsions of the Jews in the Middle East and North Africa because they have a hard time calling non-White Mizrahi and Sephardi Jews “European Colonialists.” They frequently confuse Ethiopian Jewish Israeli Citizens with Eritrean Refugees because they don’t understand the fundamental and important differences between the two groups and they don’t want to put in the effort to learn about either so long as they can condemn Israel for something.
6. Fighting Anti-Semitism Isn’t Seen as “Cool”. Fighting anti-semitism isn’t going to get your posts thousands upon thousands of notes. You’re more likely to get those results posting Hitler’s home movies. People who are motivated by tumblr fame don’t see a lot of popular posts about anti-semitism and therefore don’t think it’s worth the effort to get involved. Notice that popular posts about anti-semitism tend to be piling on celebrities they hate for other reasons or stuff that is bashing Nazis because everyone hates Nazis because, among other things, they’re White Supremacists. But dealing with contemporary anti-semitism? Especially as it manifests itself so frequently in contemporary social justice circles? It’s more likely to lose you followers than win you any. And as much as people on tumblr like to pretend that they’re trendsetters and iconoclasts, they’ve merely selected a different avenue for their groupthink. True iconoclasts will fight for something when it’s unpopular. And if you read a bit of a dare in there, it was quite intentional.