Recently, a fascinating study was published in the British Journal of Psychology on what exposure to conspiracy theories does to people.
The experiments, done in the UK, were divided into three parts. In the first, it was shown that exposure to conspiracy theories involving Muslim immigrants increased prejudice towards Muslim immigrants, which is not too surprising.
The second part exposed people to anti-Jewish conspiracy theories. It went a little beyond the first to determine that after exposed to anti-Jewish conspiracy theories (Jews were responsible for 9/11) the subjects indicated that they are less likely to vote for any Jewish candidate, meaning that it not only affected their perceptions but also their actions.
The third part is the most interesting. After the subjects were exposed to anti-Jewish conspiracy theories, their attitudes towards other unrelated groups became more prejudiced. In other words, what starts with Jews doesn't end with Jews.
In Study 3, we provide the first evidence that exposure to conspiracy theories not only increases prejudice towards the outgroup implicated in the alleged conspiracy but also towards other, uninvolved outgroups. Specifically, our results point to an indirect effect, such that exposure to conspiracy theories relating to Jewish people increases prejudice towards secondary outgroups via increases in prejudice towards Jewish people. This spreading of prejudiced attitudes was apparent across a range of different outgroups including Americans, Arabs, the elderly, poor people, and people on benefits. Previous findings suggest that transfer effects emerge most strongly for groups that are perceived to be similar to the primary outgroup, and least strongly to dissimilar groups (Harwood et al., 2011). Interestingly, if we adopt a stereotype content model perspective (Fiske, Cuddy, Glick, & Xu, 2002) we can see that, generally, indirect effects were strongest for groups that, along with Jewish people, are classified as high in competence (e.g., Asians, Irish, Americans, Australians) as opposed to low competence groups (e.g., the elderly, poor people, people on benefits). Ultimately, however, findings suggest the consequences of exposure to conspiracy theories for intergroup relations may be much broader than originally conceived, and capable of reducing more widespread intergroup tolerance.If I may take these conclusions a bit further, it would indicate that conspiracy theories about Zionists or Israelis cannot but increase antisemitism, because Jews are the closest outgroup to Zionists. Indeed, AMCHA has found a correlation between BDS on campus and antisemitic activities on campus, and while that study did not center on conspiracy theories, it did indicate that the "outgroups" of Zionists and Jews are considered closely related by people and therefore the effects of hearing lies about one will affect attitudes towards the other.
The relevance, of course, is that the idea that - for example - AIPAC controls Congress, which is a conspiracy theory, will inevitably increase prejudice against not only Zionists but towards Jews. This is instinctively felt by most Jews which is the reason for the outrage over Ilhan Omar's comments, but worse than that is the sober-sounding articles that followed the news story where the New York Times and other news outlets "confirmed" the conspiracy theory of a shadowy group of people controlling and manipulating the US government, ignoring the many other interest groups that are far more effective at lobbying than AIPAC.
The long term effects of both that conspiracy theory as well as Omar's other charge that Zionists have dual loyalty will inevitably mainstream and increase antisemitism across the board in the US.
Beyond that, this study shows that those who become prejudiced against one group as a result of exposure to conspiracy theories generally become prejudiced towards other groups as well. No matter what political party or philosophy you belong to, exposure to hate affects one's attitudes across the board.
(h/t MtTB)