I've been hearing from Jewish friends I respect, even before the Pittsburgh shooting, that they perceive that anti-Semitism is on the rise in the U.S. These friends have disparate ideological views; some are on the left, some on the right politically.
As I've noted before, the data don't (yet?) support a significant increase in American anti-Semitism. The ADL regularly polls American attitudes toward Jews. The most recent survey was conducted in late October 2016, at the heart of a bitter election campaign that some argue was infected with anti-Semitism. The rate of anti-Semitism found was 14%, within the same 12 to 15% bound it's been in ADL studies since 2004. (I've debunked the notion that there has been a 60% rise in anti-Semitic incidents elsewhere, but it's possible that there has been some increase in incidents.)
Let's assume in the absence of contrary data that there has not been a significant, or perhaps any, increase in anti-Semitic attitudes among Americans. Why might Jewish Americans still fell under increased threat from anti-Semitism?
I can't rule out moral panic, but I think there is a better explanation. Let's begin with some background, starting with the fact that many Jews reasonably see themselves as vulnerable population; the Holocaust is always in the back of our minds, and we notice, even if most Americans don't, that Jews are by far the religious group most targeted by hate crimes. The security guards and truck bomb barriers at Jewish institutions are a constant reminder of the threat of anti-Semitic violence.
Let's add that American Jews notice very negative trends in Europe. The Jewish right sees what's going on in places like Sweden, France, and Great Britain (where the formerly mainstream center-left Labour Party has been taken over by leftist anti-Semites) and fears that nascent anti-Semitism on the anti-Israel left will eventually lead to a similar situation in the U.S The Jewish left sees the rise of anti-Semitic neo-fascist parties in Europe and worries about the U.S. heading in that direction. Less ideologically driven Jews are justifiably concerned about both phenomena.
It doesn't help that neither the mainstream American right or left exhibits much sensitivity to Jewish concerns about anti-Semitism. On the right, the common response is that "we're pro-Israel, what do you want from us?" Meanwhile, the Jewish sense of vulnerability is positively disparaged on the left, which considers being Jewish in the U.S. to at best a subset of "white privilege." (Lefist Jews themselves are not immune from the latter; consider this sermon by a Reform rabbi about his white privilege, in which he conclude that being "both Jewish and white puts us in the perfect place be make a positive difference, by being allies with those who experience discrimination." Note that he seems to assume that Jews themselves never experience discrimination.)
That background, while important, doesn't explain Jews' sense of increased anti-Semitism in the U.S. I think the best explanation for that sense is that even if the percentage of anti-Semites in the American public hasn't increased, they are more active, more visible, and more willing to express their views publicly.
- More Active
On the right, the internet has given anti-Semites a way of much more easily coordinating than they had in the days of handprinted newsletters and secretive meetings in Days Inn conference rooms. On the left, the rise of hostility to Israel as a major issue for the left has given anti-Semites an opportunity to spread anti-Semitism in the guise of "anti-Zionism".
- More Visible
Not too long ago, expression of anti-Semitic sentiments was suppressed by media gatekeepers; mainstream news organizations wouldn't publish anti-Semites, nor would respectable journals of opinion. But now the gatekeepers are in a free-for-all market, and they can't control what is said on blogs, websites, etc., and their own editorial standards have declined. Twitter gives an easy public forum for anti-Semites. And the comments sections of most sites are unmoderated, providing a forum for anti-Semites regardless of the editorial perspective of the site. You won't find a site with more philo-Semitic site than Instapundit, for example, but you will still see some anti-Semitism in the comments. Even this blog, written mostly by Jews, attracts its share of anti-Semitic commentators, more so when it was hosted by the Washington Post.
- More Willing to Express their Views Publicly
In our polarized times, the left and right are much less willing to police their "own," focusing instead only on the sins of the other side. The result, for example, is that Harvard and University Chicago professors can publish an entire book that is essentially a long anti-Semitic conspiracy theory, without any damage to their careers or reputation, because the book served the purposes of the political left. Donald Trump can retweet anti-Semitic imagery, not apologize for doing so, and not have any political consequences. Another factor is immigration from the Middle East. Middle Eastern immigrants are arriving from societies in which anti-Semitism is widely accepted, so it's not surprising that Middle Eastern university students who, for example, join Students for Justice in Palestine, are sometimes not embarrassed to engage in openly anti-Semitic rhetoric.
Making matters worse, there is no longer any widely respected anti-Semitism watchdog in the United States. The ADL is disparaged by the right for its drastically increased partisanship since a Democratic operative took over its leadership. The left rejects the ADL because it advocates for Israel, and refuses to adhere to the increasingly common claim that anti-Zionism is essentially never anti-Semitic. The ADL's upstart competitors, such as the Southern Poverty Law Center and the Anne Frank Center, are even more relentlessly ideological and partisan.